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Operators constitute the basic building block of any programming language. Java too provides many types of operators which can be used according to the need to perform various calculations and functions, be it logical, arithmetic, relational, etc. They are classified based on the functionality they provide.

Types of Operators: 

• Arithmetic Operators
• Unary Operators
• Assignment Operator
• Relational Operators
• Logical Operators
• Ternary Operator
• Bitwise Operators
• Shift Operators

This article explains all that one needs to know regarding Assignment Operators. 

Assignment Operators

These operators are used to assign values to a variable. The left side operand of the assignment operator is a variable, and the right side operand of the assignment operator is a value. The value on the right side must be of the same data type of the operand on the left side. Otherwise, the compiler will raise an error. This means that the assignment operators have right to left associativity, i.e., the value given on the right-hand side of the operator is assigned to the variable on the left. Therefore, the right-hand side value must be declared before using it or should be a constant. The general format of the assignment operator is, 

Types of Assignment Operators in Java

The Assignment Operator is generally of two types. They are:

1. Simple Assignment Operator: The Simple Assignment Operator is used with the “=” sign where the left side consists of the operand and the right side consists of a value. The value of the right side must be of the same data type that has been defined on the left side.

2. Compound Assignment Operator: The Compound Operator is used where +,-,*, and / is used along with the = operator.

Let’s look at each of the assignment operators and how they operate: 

1. (=) operator: 

This is the most straightforward assignment operator, which is used to assign the value on the right to the variable on the left. This is the basic definition of an assignment operator and how it functions. 

Syntax:  

Example:  

2. (+=) operator: 

This operator is a compound of ‘+’ and ‘=’ operators. It operates by adding the current value of the variable on the left to the value on the right and then assigning the result to the operand on the left. 

Note: The compound assignment operator in Java performs implicit type casting. Let’s consider a scenario where x is an int variable with a value of 5. int x = 5; If you want to add the double value 4.5 to the integer variable x and print its value, there are two methods to achieve this: Method 1: x = x + 4.5 Method 2: x += 4.5 As per the previous example, you might think both of them are equal. But in reality, Method 1 will throw a runtime error stating the “i ncompatible types: possible lossy conversion from double to int “, Method 2 will run without any error and prints 9 as output.

Reason for the Above Calculation

Method 1 will result in a runtime error stating “incompatible types: possible lossy conversion from double to int.” The reason is that the addition of an int and a double results in a double value. Assigning this double value back to the int variable x requires an explicit type casting because it may result in a loss of precision. Without the explicit cast, the compiler throws an error. Method 2 will run without any error and print the value 9 as output. The compound assignment operator += performs an implicit type conversion, also known as an automatic narrowing primitive conversion from double to int . It is equivalent to x = (int) (x + 4.5) , where the result of the addition is explicitly cast to an int . The fractional part of the double value is truncated, and the resulting int value is assigned back to x . It is advisable to use Method 2 ( x += 4.5 ) to avoid runtime errors and to obtain the desired output.

Same automatic narrowing primitive conversion is applicable for other compound assignment operators as well, including -= , *= , /= , and %= .

3. (-=) operator: 

This operator is a compound of ‘-‘ and ‘=’ operators. It operates by subtracting the variable’s value on the right from the current value of the variable on the left and then assigning the result to the operand on the left. 

4. (*=) operator:

 This operator is a compound of ‘*’ and ‘=’ operators. It operates by multiplying the current value of the variable on the left to the value on the right and then assigning the result to the operand on the left. 

5. (/=) operator: 

This operator is a compound of ‘/’ and ‘=’ operators. It operates by dividing the current value of the variable on the left by the value on the right and then assigning the quotient to the operand on the left. 

6. (%=) operator: 

This operator is a compound of ‘%’ and ‘=’ operators. It operates by dividing the current value of the variable on the left by the value on the right and then assigning the remainder to the operand on the left. 

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Assignment, Arithmetic, and Unary Operators

The simple assignment operator.

One of the most common operators that you'll encounter is the simple assignment operator " = ". You saw this operator in the Bicycle class; it assigns the value on its right to the operand on its left:

This operator can also be used on objects to assign object references , as discussed in Creating Objects .

The Arithmetic Operators

The Java programming language provides operators that perform addition, subtraction, multiplication, and division. There's a good chance you'll recognize them by their counterparts in basic mathematics. The only symbol that might look new to you is " % ", which divides one operand by another and returns the remainder as its result.

The following program, ArithmeticDemo , tests the arithmetic operators.

This program prints the following:

You can also combine the arithmetic operators with the simple assignment operator to create compound assignments . For example, x+=1; and x=x+1; both increment the value of x by 1.

The + operator can also be used for concatenating (joining) two strings together, as shown in the following ConcatDemo program:

By the end of this program, the variable thirdString contains "This is a concatenated string.", which gets printed to standard output.

The Unary Operators

The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.

The following program, UnaryDemo , tests the unary operators:

The increment/decrement operators can be applied before (prefix) or after (postfix) the operand. The code result++; and ++result; will both end in result being incremented by one. The only difference is that the prefix version ( ++result ) evaluates to the incremented value, whereas the postfix version ( result++ ) evaluates to the original value. If you are just performing a simple increment/decrement, it doesn't really matter which version you choose. But if you use this operator in part of a larger expression, the one that you choose may make a significant difference.

The following program, PrePostDemo , illustrates the prefix/postfix unary increment operator:

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• A named space for holding data/information
• The name is often referred to as the identifier
• A representation of a datum
• A symbol indicating that an operation is to be performed (on one or more operands)
• A combination of variables, operators, and literals that represent a single value
• The smallest syntactically valid construct that conveys a complete command
• Placing a value into the memory identified by a variable/constant
• The assignment operator is a binary operator; the left-side operand is a variable/constant and the right-side operand is a literal or an expression (i.e., something that evaluates to a value)
• initial = 'H'
• initial = 'H';
• ok = false;
• A variable can only contain one value at a time
• int i; i = 5; // i contains the value 5 i = 27; // i now contains the value 27
• Confusing the assignment operator with the notion of "equality"
• Attempting to use expressions like 21 = age (which has an inappropriate left-side operand)
• The assignment operation evaluates to the value of the right-side operand (so, is an expression)
• int i, j; i = j = 5;
• It can cause confusion in more complicated statements, especially those involving arithmetic operators and relational operators
• In the previous example, which assignment is performed first?
• Associativity - determines whether (in the absence of other determinants) an expression is evaluated from left to right or right to left
• The assignment operator has right to left associativity, so i = j = 5 is equivalent to i = (j = 5)
• Ensuring that the type of the right-side operand is the same as the type of the left-side operand
• Java does not allow implicit losses of precision
• Java does allow widenings (though you should refrain from using them)
• double weight; int age; age = 21.0; // Not allowed (will generate a compile-time error) weight = 155; // Allowed but not recommended (use 155. instead)
• ( type ) expression
• Examples: double real; int small; long large; // ... small = (int)large; // ... small = (int)real;
• Loss of precision
• Possible loss of magnitude
• Possible change of sign
• Indicate that a value can only be assigned to a variable once
• final type variable [, variable ]... ;
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• Same as for other variables
• Must be all uppercase
• Underscores between "words" improve readability
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• Bitwise Logical Operators     >>

Symbols used for mathematical and logical manipulation that are recognized by the compiler are commonly known as operators in Java. In the third of five lessons on operators we look at the assignment operators available in Java.

Assignment Operators Overview  Top

The single equal sign = is used for assignment in Java and we have been using this throughout the lessons so far. This operator is fairly self explanatory and takes the form variable = expression; . A point to note here is that the type of variable must be compatible with the type of expression .

Shorthand Assignment Operators

The shorthand assignment operators allow us to write compact code that is implemented more efficiently.

Automatic Type Conversion, Assignment Rules  Top

The following table shows which types can be assigned to which other types, of course we can assign to the same type so these boxes are greyed out.

When using the table use a row for the left assignment and a column for the right assignment. So in the highlighted permutations byte = int won't convert and int = byte will convert.

Casting Incompatible Types  Top

The above table isn't the end of the story though as Java allows us to cast incompatible types. A cast instructs the compiler to convert one type to another enforcing an explicit type conversion.

A cast takes the form     target = (target-type) expression .

There are a couple of things to consider when casting incompatible types:

• With narrowing conversions such as an int to a short there may be a loss of precision if the range of the int exceeds the range of a short as the high order bits will be removed.
• When casting a floating-point type to an integer type the fractional component is lost through truncation.
• The target-type can be the same type as the target or a narrowing conversion type.
• The boolean type is not only incompatible but also inconvertible with other types.

Lets look at some code to see how casting works and the affect it has on values:

Running the Casting class produces the following output:

The first thing to note is we got a clean compile because of the casts, all the type conversions would fail otherwise. You might be suprised by some of the results shown in the screenshot above, for instance some of the values have become negative. Because we are truncating everything to a byte we are losing not only any fractional components and bits outside the range of a byte , but in some cases the signed bit as well. Casting can be very useful but just be aware of the implications to values when you enforce explicit type conversion.

Related Quiz

Fundamentals Quiz 8 - Assignment Operators Quiz

Lesson 9 Complete

In this lesson we looked at the assignment operators used in Java.

What's Next?

In the next lesson we look at the bitwise logical operators used in Java.

Getting Started

Code structure & syntax, java variables, primitives - boolean & char data types, primitives - numeric data types, method scope, arithmetic operators, relational & logical operators, assignment operators, assignment operators overview, automatic type conversion, casting incompatible types, bitwise logical operators, bitwise shift operators, if construct, switch construct, for construct, while construct.

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Assignment operators in java: an overview.

We already discussed the Types of Operators in the previous tutorial Java. In this Java tutorial , we will delve into the different types of assignment operators in Java, and their syntax, and provide examples for better understanding. Because Java is a flexible and widely used programming language. Assignment operators play a crucial role in manipulating and assigning values to variables. To further enhance your understanding and application of Java assignment operator's concepts, consider enrolling in the best Java Certification Course .

What are the Assignment Operators in Java?

Assignment operators in Java are used to assign values to variables . They are classified into two main types: simple assignment operator and compound assignment operator.

The general syntax for a simple assignment statement is:

And for a compound assignment statement:

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Types of Assignment Operators in Java

• Simple Assignment Operator: The Simple Assignment Operator is used with the "=" sign, where the operand is on the left side and the value is on the right. The right-side value must be of the same data type as that defined on the left side.
• Compound Assignment Operator:  Compound assignment operators combine arithmetic operations with assignments. They provide a concise way to perform an operation and assign the result to the variable in one step. The Compound Operator is utilized when +,-,*, and / are used in conjunction with the = operator.

1. Simple Assignment Operator (=):

The equal sign (=) is the basic assignment operator in Java. It is used to assign the value on the right-hand side to the variable on the left-hand side.

Explanation

2. addition assignment operator (+=) :, 3. subtraction operator (-=):, 4. multiplication operator (*=):.

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5. Division Operator (/=):

6. modulus assignment operator (%=):, example of assignment operator in java.

Let's look at a few examples in our Java Playground to illustrate the usage of assignment operators in Java:

• Unary Operator in Java
• Arithmetic Operators in Java
• Relational Operators in Java
• Logical Operators in Java
• Ternary Operator in Java

Q1. Can I use multiple assignment operators in a single statement?

Q2. are there any other compound assignment operators in java, q3. how many types of assignment operators.

• 1. (=) operator
• 1. (+=) operator
• 2. (-=) operator
• 3. (*=) operator
• 4. (/=) operator
• 5. (%=) operator

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Java provides many types of operators to perform a variety of calculations and functions, such as logical , arithmetic , relational , and others. With so many operators to choose from, it helps to group them based on the type of functionality they provide. This programming tutorial will focus on Java’s numerous a ssignment operators.

Before we begin, however, you may want to bookmark our other tutorials on Java operators, which include:

• Arithmetic Operators
• Comparison Operators
• Conditional Operators
• Logical Operators
• Bitwise and Shift Operators

Assignment Operators in Java

As the name conveys, assignment operators are used to assign values to a variable using the following syntax:

The left side operand of the assignment operator must be a variable, whereas the right side operand of the assignment operator may be a literal value or another variable. Moreover, the value or variable on the right side must be of the same data type of the operand on the left side. Otherwise, the compiler will raise an error. Assignment operators have a right to left associativity in that the value given on the right-hand side of the operator is assigned to the variable on the left. Therefore, the right-hand side variable must be declared before assignment.

You can learn more about variables in our programming tutorial: Working with Java Variables .

Types of Assignment Operators in Java

Java assignment operators are classified into two types: simple and compound .

The Simple assignment operator is the equals ( = ) sign, which is the most straightforward of the bunch. It simply assigns the value or variable on the right to the variable on the left.

Compound operators are comprised of both an arithmetic, bitwise, or shift operator in addition to the equals ( = ) sign.

Equals Operator (=) Java Example

First, let’s learn to use the one-and-only simple assignment operator – the Equals ( = ) operator – with the help of a Java program. It includes two assignments: a literal value to num1 and the num1 variable to num2 , after which both are printed to the console to show that the values have been assigned to the numbers:

The += Operator Java Example

A compound of the + and = operators, the += adds the current value of the variable on the left to the value on the right before assigning the result to the operand on the left. Here is some sample code to demonstrate how to use the += operator in Java:

The -= Operator Java Example

Made up of the – and = operators, the -= first subtracts the variable’s value on the right from the current value of the variable on the left before assigning the result to the operand on the left. We can see it at work below in the following code example showing how to decrement in Java using the -= operator:

The *= Operator Java Example

This Java operator is comprised of the * and = operators. It operates by multiplying the current value of the variable on the left to the value on the right and then assigning the result to the operand on the left. Here’s a program that shows the *= operator in action:

The /= Operator Java Example

A combination of the / and = operators, the /= Operator divides the current value of the variable on the left by the value on the right and then assigns the quotient to the operand on the left. Here is some example code showing how to use the  /= operator in Java:

%= Operator Java Example

The %= operator includes both the % and = operators. As seen in the program below, it divides the current value of the variable on the left by the value on the right and then assigns the remainder to the operand on the left:

Compound Bitwise and Shift Operators in Java

The Bitwise and Shift Operators that we just recently covered can also be utilized in compound form as seen in the list below:

• &= – Compound bitwise Assignment operator.
• ^= – Compound bitwise ^ assignment operator.
• >>= – Compound right shift assignment operator.
• >>>= – Compound right shift filled 0 assignment operator.
• <<= – Compound left shift assignment operator.

The following program demonstrates the working of all the Compound Bitwise and Shift Operators :

Final Thoughts on Java Assignment Operators

This programming tutorial presented an overview of Java’s simple and compound assignment Operators. An essential building block to any programming language, developers would be unable to store any data in their programs without them. Though not quite as indispensable as the equals operator, compound operators are great time savers, allowing you to perform arithmetic and bitwise operations and assignment in a single line of code.

Read more Java programming tutorials and guides to software development .

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Common Syntax Errors In Java And The Ultimate Guide To Avoid Them

Table of contents.

You must be meticulous when writing code to avoid errors and make sure your programs work, especially when it comes to the syntax of your chosen coding language. Syntax errors in Java may be particularly difficult if you’re not used to the language. Java is not known to be accessible or beginner-friendly compared to a  language such as Python . Making mistakes, especially syntax mistakes, is common.

There are several common syntax errors in Java you may run into while programming. When you know what to expect, you can take measures to avoid these syntax errors in Java and other mistakes.

What Are Syntax Errors in Programming?

Every programming language has unique rules of grammar called its syntax, though some may share similarities with other languages. The  syntax of a programming language  dictates what a valid expression or statement looks like. The code will only run if you write it with a valid syntax. Otherwise, the code’s compiler or interpreter will not understand the statement, generating a syntax error.

High-level languages (Java, C++, and Python) have more human-readable syntax compared to low-level languages, such as assembly language, which have less abstraction.

Take the following code snippets written in several programming languages. In each example, a simple “find” program designed to locate a word in a sentence uses “if” statements and built-in functions such as “in,” “find,” and “contains.” If the target word is found, a sentence is printed in the console, indicating that the computer program found the word.

Java syntax

String mySentence = “The quick brown fox jumped over the lazy dog.”; String wordToFind = “fox”; if (mySentence.contains(wordToFind)) { System.out.println(“I found the word ‘” + wordToFind + “‘ in the sentence.”); }

Python syntax

my_sentence = “The quick brown fox jumped over the lazy dog.” word_to_find = “fox” if word_to_find in my_sentence: print(f”I found the word ‘{word_to_find}’ in the sentence.”)

#include <iostream> #include <string> using namespace std; int main() { string mySentence = “The quick brown fox jumped over the lazy dog.”; string wordToFind = “fox”; if (mySentence.find(wordToFind) != string::npos) { cout << “I found ‘” << wordToFind << “‘ in the sentence.” << endl; } return 0; }

Each language writes the program with unique syntax even though they perform the same task (in this case, looking for a word in a sentence). Note how sentences are structured, the indentations, and the symbols used. These elements make up the syntax for a programming language.

You can see some of the differences in the syntax of each language in these short examples. The differences are even more apparent when looking at longer, much more complex programs.

The differences between languages in the examples above include:

• Declaration of variables:  Dynamic typing is allowed in Python, with the string “my_sentence” not explicitly declared. In Java and C++, the string type must be declared: “String mySentence” and “string mySentence.”
• Naming conventions:  Python has all lowercase names with underscores instead of spaces — known as snake case. Java and C++ lowercase the first word, have no spaces, and capitalize words after the first word — known as camel case.
• Indentation:  Python uses indentation for each code block, whereas Java and C++ use curly braces.
• Punctuation:  Java and C++ require semicolons to end each line, while Python does not.
• Printing to the console or terminal:  The syntax for printing to the console differs, as shown in the last few lines of each example above.

If you write a program in one language and forget to use the symbols and syntax required, you will get a syntax error if you try to run the program.

For example, say you forget the colon at the end of the “if” statement in a Python program. If you are running the program in Integrated Development and Learning and Environment (IDLE), you will get a syntax error that indicates what was expected and on which line the error was found, as shown in the following image.

What Are Syntax Errors in Java?

When you write and run a program in Java, your computer will first attempt to compile and interpret the code you’ve written so that the code is in a format the computer can understand. The Java Compiler will alert you of syntax errors in Java programs before they are completely compiled and run.

The Java Compiler first compiles Java code into bytecode. The Java Virtual Machine (JVM) then converts the bytecode into a usable program that can be run on the local hardware.

This can be done on different systems. Java is a multiplatform language that can run on desktop platforms, mobile platforms, web browsers, and any platform with a JVM installed. You don’t have to write a different program from Windows, Mac, web browsers, or anywhere else you want to run your code.

For example, if you want to write a web-scraping app in Java, you can use that app on multiple platforms without changing the code.

If you do not write your code using the  appropriate Java syntax , you will get syntax errors in the Java programs you attempt to run, regardless of what platform you use.

Examples of syntax errors in Java code

Some  common Java syntax errors  you may run into while programming Java include:

Undeclared variables

• Missing colons, brackets, or parentheses
• Omitting a semicolon at the end of a line

Misspelled keywords

• Incorrect capitalization (Java is case-sensitive)
• Mismatched quotes, such as starting a string with a single quote and ending in a double quote
• Variable name errors, such as starting a variable with a number
• Incorrectly declaring methods, such as not using curly braces
• Incorrect use of mathematical operators
• Invalid type casting (attempting to convert one type to another)
• Incorrect data types, such as int, float, or boolean
• Improper control structure for statements such as if, else, or switch statements
• Failing to import a class
• Omitting the word “break” in a switch statement
• Forgetting to include a “return” statement

These are just a few of the syntax errors in Java programming. If you’re learning the language, make sure to study it closely to avoid making similar syntax errors in Java.

Java Errors and Solutions

Before you can solve Java errors, you need to make sure you have your system properly set up in the first place. Java programming requires one of the latest Java Editions, such as the Java Standard Edition (Java SE), the Java Enterprise Edition (EE), or the Java Micro Edition (ME). You will also need the Java Development Kit (JDK) and an interactive development environment (IDE) like Eclipse or JetBrains to write your code. If you have all of the above correctly installed on your system, you should be able to write and run Java programs.

Debugging your code in the IDE is a useful method for catching syntax errors in Java programs. You can run and debug the following code in Eclipse.

After making a new project and class, you will have your main function into which you can write a common such as “print line” to output a line of text into the console window of Eclipse:

package com.myprogram; public class myClass { public static void main(String[] args) { // TODO Auto-generated method stub System.out.println(“Hello, world”); } } You can run a simple “Hello, world” program to make sure everything works. Your IDE will alert you if anything is wrong with your package or the code in your Main class and recommend a solution.

Using an IDE such as Eclipse to write your program will alert you of issues that need to be resolved, as it will not run code that contains syntax errors in Java. Eclipse notifies you of syntax errors in Java as you type them.

The string “Hello, world” is the expected output to either the terminal or console when you click Run or Debug from the Run menu or choose Run [package name] from the menu toolbar. If you forget the semicolon at the end of the line with the print line function “System. out.println(“Hello, world”),” a red line appears under the mistake, and there is an error indicator next to the line number. If you hover over either the red line or the error indicator, you will see the error message: “Syntax error, insert “;” to complete BlockStatements.”

The IDE will warn you of syntax errors in Java as you write before you even debug the program. Simply hover over the error indicator or the red line under the error for a solution.

Syntax errors in Java web scraper code

You may run into several syntax errors in Java when  web scraping . Consider the following Java code for a basic web scraper   program that finds the title of a web page and exports it into a text document. It is a longer and more complex program than the earlier examples. It’s not uncommon to have more than one syntax error in Java programs like this.

package com.example.scraper; import java.io.BufferedWriter; import java.io.FileWriter; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Scraper { public static void main(String[] args) { String url = “https://lite.cnn.com”; try { URL cnnUrl = new URL(url); HttpURLConnection connection = (HttpURLConnection) cnnUrl.openConnection(); InputStream inputStream = connection.getInputStream(); InputStreamReader myReader = new InputStreamReader(inputStream); Scanner myScanner = new Scanner(myReader); BufferedWriter myWriter = new BufferedWriter(new FileWriter(“C:/path/to/file/title.txt”)); Pattern myTitlePattern = Pattern.compile(“<title>(.*?)</title>”); while (myScanner .hasNextLine()) { String line = myScanner .nextLine(); Matcher matcher = myTitlePattern.matcher(line); while (matcher.find()) { String titleText = matcher.group(1); myWriter .write(titleText); myWriter .newLine(); } } myWriter .close(); myScanner .close(); System.out.println(“Scraping complete.”); } catch (IOException e) { e.printStackTrace(); } } } This code scrapes the website https://lite.cnn.com, a condensed and simplified version of the CNN news homepage. The program will find the title of the page and save it to a text file.

The following are some examples of syntax errors in Java code you may run into in the example program above.

Missing curly brace

If you forgot a curly brace opening up the main method and you ran the program in Eclipse, you will get this syntax error:

Exception in thread “main” java.lang.Error: Unresolved compilation problem:

Syntax error on token”)”, { expected after this token

at Scraper/com.example.scraper.Scraper.main(Scraper.java:15)

Missing parentheses

If you forget a parenthesis, you will get the following syntax error:

Syntax error on token “Scannerreader”, ( expected after this token

at Scraper/com.example.scraper.Scraper.main(Scraper.java:24)

Missing equals sign

If you leave out an equals sign, you will get this syntax error:

Syntax error on token “connection”, = expected after this token

at Scraper/com.example.scraper.Scraper.main(Scraper.java:20)

If you don’t declare the variable “URL” to be a String, you’ll get the following error:

Exception in thread “main” java.lang.Error: Unresolved compilation problems:

url cannot be resolved to a variable

at Scraper/com.example.scraper.Scraper.main(Scraper.java:16)

If you misspell a keyword, such as the word “Pattern,” on line 29, you will get the following error:

Patern cannot be resolved

at Scraper/com.example.scraper.Scraper.main(Scraper.java:29)

Assignment errors

If you leave out the left part of an assignment, such as the word “if” on line 31, you will get syntax errors such as this error:

The left-hand side of an assignment must be a variable

Syntax error, insert “AssignmentOperator Expression” to complete Assignment

Syntax error, insert “;” to complete Statement

at Scraper/com.example.scraper.Scraper.main(Scraper.java:31)

Double quotes for strings missing

Strings need to be surrounded by double quotes, such as the string of the website you want to scrape on line 16. If you leave them out, you will get an “unresolved” syntax error in Java:

https cannot be resolved to a variable

Syntax error on token “:”, ; expected

“Try and catch” syntax error

In the try-and-catch block of the program, you need to have the “catch” part of the statement. Whether you misspell the word or leave it out altogether, you will get a syntax error:

Syntax error on token “caught”, catch expected

at Scraper/com.example.scraper.Scraper.main(Scraper.java:47)

Parameter error

On the same line, the parameter “e” is expected in the “catch” statement. A syntax error will occur if you leave it out or misspell the parameter:

Syntax error, insert “VariableDeclaratorId” to complete FormalParameter

e cannot be resolved

Case sensitive error

Java is case-sensitive, so you will get an error if you lowercase “System” on line 45:

system cannot be resolved

at Scraper/com.example.scraper.Scraper.main(Scraper.java:45)

Type mismatch error

In Java, you need to declare a variable type when initializing variables. If you put “int,” short for integer, instead of “String” for the string “URL,” you will get a type mismatch error:

Type mismatch: cannot convert from String to int

The constructor URL(int) is undefined

Misspelled variable

If you misspell or otherwise use the wrong variable name for a variable that you have declared, you will get an unresolved compilation problem. For example, using the variable “writers” on line 42 without declaring a variable called “writers:”

writers cannot be resolved

at Scraper/com.example.scraper.Scraper.main(Scraper.java:42)

Invalid assignment operator

If you attempt to assign a variable, such as “c = a /b,” but you do not include the proper assignment operator “=”, you will get an invalid assignment operator syntax error:

Syntax error on token “/”, invalid AssignmentOperator

Invalid mathematical function errors

Syntax errors in Java are often caused by misspelling a word or typing the wrong symbol, including a mathematical operator. If you make an error in a math equation (such as accidentally dividing an integer by zero because you put the wrong variable in the wrong place), you will get an arithmetic error:

Exception in thread “main” java.lang.ArithmeticException: / by zero

Splitting a string on two lines

If you attempt to split a string on more than one line without properly concatenating it (by breaking the string into two with a plus sign between them), you will get a syntax error. For example:

Syntax error on token “”to/headlines.txt””, delete this token

at Scraper/com.example.scraper.Scraper.main(Scraper.java:27)

Mistyping the main method

If you misspell or make an error writing the exact words Java expects when writing the header for the main method, you will get a syntax error explaining that the main method should look exactly like this: “public static void main(String[] args)” with no variation. For example:

Error: Main method is not static in class com.example.scraper.Scraper, please define the main method as:

public static void main(String[] args)

You can see in the above examples that when there are syntax errors in Java programs, your IDE:

• Gives you the error name, such as “Unresolved compilation problem: Syntax error.”
• Provides what is the best solution, such as “{ expected after this token.”
• Tells you the location of the error — for example, “Scraper.java:20,” meaning the error is on line 20 of the program.

You can fix the syntax errors in Java by noting the location of the errors and making the recommended changes.

The above errors are just a few syntax errors in Java you may run into. There are many resources out there to help you learn more about syntax errors in Java and other common issues.

Other types of errors

Syntax errors in Java are only  one type of error . Some other errors in Java you may run across include:

• Java: error: release version 19 not supported error:  This error means you are targeting a Java version, such as version 19, not supported by your JDK.
• .Class expected error in Java error:  You may get this syntax error if you make a mistake with a class or object.
• Java: error: release version 5 not supported:  Make sure you have the latest Java version supported by your JDK.
• Run-time error Java error:  Run-time errors are exceptions that occur while the program is running, as opposed to syntax errors in Java programs that occur during compilation.

Syntax errors in Java are relatively easy to solve because they are caught before the program is fully compiled. This allows you to fix the error on the fly, compared to errors like the ones above, which often make it past compilation.

One way to catch all errors in Java is to put your entire program inside a try-and-catch block. Try-and-catch blocks do not catch syntax errors because the compiler or interpreter would catch the syntax errors in Java before the program could be run. But they can be useful for other errors.

The “try and catch” block in the example web scraper code from earlier starts at line 19 and includes all of the code up to line 46. Immediately after the word “catch” in line 46 is the line of code that will run if there is an error, known as an exception. This code handles errors that may come up during the program’s execution. If an error occurs, the exceptions catch it and execute the code in the “catch” block.

Get More Programming and Web Scraping Help From Rayobyte

You can easily resolve syntax errors in Java compared to other types of errors. Fixing and preventing syntax errors in Java programs is as simple as reviewing notifications in your IDE and noting the specific syntax errors in Java it highlights when you attempt to run the program.

If you want to learn more about fixing syntax errors in Java, web scraping, and how to  use proxies to hide your IP  so you can scrape without getting blocked,  visit our blog  for all sorts of proxy-related information or  get in touch today .

The information contained within this article, including information posted by official staff, guest-submitted material, message board postings, or other third-party material is presented solely for the purposes of education and furtherance of the knowledge of the reader. All trademarks used in this publication are hereby acknowledged as the property of their respective owners.

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How to fix SyntaxError: invalid assignment left-hand side

by Nathan Sebhastian

Posted on Jul 10, 2023

Reading time: 3 minutes

When running JavaScript code, you might encounter an error that says:

Both errors are the same, and they occured when you use the single equal = sign instead of double == or triple === equals when writing a conditional statement with multiple conditions.

Let me show you an example that causes this error and how I fix it.

How to reproduce this error

Suppose you have an if statement with two conditions that use the logical OR || operator.

You proceed to write the statement as follows:

When you run the code above, you’ll get the error:

This error occurs because you used the assignment operator with the logical OR operator.

An assignment operator doesn’t return anything ( undefined ), so using it in a logical expression is a wrong syntax.

How to fix this error

To fix this error, you need to replace the single equal = operator with the double == or triple === equals.

Here’s an example:

By replacing the assignment operator with the comparison operator, the code now runs without any error.

The double equal is used to perform loose comparison, while the triple equal performs a strict comparison. You should always use the strict comparison operator to avoid bugs in your code.

Other causes for this error

There are other kinds of code that causes this error, but the root cause is always the same: you used a single equal = when you should be using a double or triple equals.

For example, you might use the addition assignment += operator when concatenating a string:

The code above is wrong. You should use the + operator without the = operator:

Another common cause is that you assign a value to another value:

This is wrong because you can’t assign a value to another value.

You need to declare a variable using either let or const keyword, and you don’t need to wrap the variable name in quotations:

You can also see this error when you use optional chaining as the assignment target.

For example, suppose you want to add a property to an object only when the object is defined:

Here, we want to assign the age property to the person object only when the person object is defined.

But this will cause the invalid assignment left-hand side error. You need to use the old if statement to fix this:

Now the error is resolved.

The JavaScript error SyntaxError: invalid assignment left-hand side occurs when you have an invalid syntax on the left-hand side of the assignment operator.

This error usually occurs because you used the assignment operator = when you should be using comparison operators == or === .

Once you changed the operator, the error would be fixed.

I hope this tutorial helps. Happy coding!

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Invalid AssignmentOperator used in lecture?

Hi , first of all, the lectures are pretty good but there is something which does not work with Java when following the coding examples.

In the 5. Video of the Ulitmate Java 1 Fundamentls path, there is an error or I do not possess the new Java version? In the lecture video about - Primitive vs Reference Types at 3:30 min I have not been able to reproduce your code line without getting a syntax error. The object’s assignment, which looks alike in javascript, does not work in my case and throws syntax error:

Point(x:1,y:2) assignment throws a syntax error:

I would like to know why this assignment operation does not work in my case ? I use VS Code and additional extensions but not the IDE like Mosh uses. Thank you very much in advance,

Problem resovled:

There can be only one public class in the same source file, otherwise the class has to be defined in another source file and then can be intstansiated in the public main class.

This error actually comes up all the time. He is not literally typing the parameter name or the colon. The IDE adds these just to make it easier to read the code.

Hi, thank you for the answer, but actually, the problem was that I didn’t import the right java package. It worked, thanks

I promise you, this syntax is invalid:

It should be this:

Thank you very much,

actually it worked after

import. But I don’t think it is clean. I use vscode and the prettier extension always renders it to the : notation, like in javascript. I don’t think it is very clean,though. Thanks and have a nice day

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TypeError: invalid assignment to const "x"

The JavaScript exception "invalid assignment to const" occurs when it was attempted to alter a constant value. JavaScript const declarations can't be re-assigned or redeclared.

What went wrong?

A constant is a value that cannot be altered by the program during normal execution. It cannot change through re-assignment, and it can't be redeclared. In JavaScript, constants are declared using the const keyword.

Invalid redeclaration

Assigning a value to the same constant name in the same block-scope will throw.

Fixing the error

There are multiple options to fix this error. Check what was intended to be achieved with the constant in question.

If you meant to declare another constant, pick another name and re-name. This constant name is already taken in this scope.

const, let or var?

Do not use const if you weren't meaning to declare a constant. Maybe you meant to declare a block-scoped variable with let or global variable with var .

Check if you are in the correct scope. Should this constant appear in this scope or was it meant to appear in a function, for example?

const and immutability

The const declaration creates a read-only reference to a value. It does not mean the value it holds is immutable, just that the variable identifier cannot be reassigned. For instance, in case the content is an object, this means the object itself can still be altered. This means that you can't mutate the value stored in a variable:

But you can mutate the properties in a variable: