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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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• Function interface has been defined with the generic types T & R , where T is the type of the input and R is the output type.
• Method apply() is the primary abstract functional method of Function interface. It takes as input a parameter t of type T and gives an output object of type R .
• Function<T, R> has two default methods. First default method compose() combines the function on which it is applied(lets call it the current function ) with another function, named before , in such a way that when the combined function is applied then first the before function is applied which converts the input type V to type T . And then the current function converts this object of type T to its output type R . Thus, the combined function obtained as a result of compose() applies both the functions, in the process converting type V to R .
• The second default method is andThen() which combines the function on which it is applied( current function ) with another function, named after , in such a way that when the combined function is called then first the current function is applied which converts the input type T to type R . And then the after function is applied which converts from type R to V . Thus, the combined function obtained by using andThen() default method applies both functions internally, in the process converting type T to type V .
• Function<T, R> also contains a static method identity() which is very simple as it returns as-is whatever is given to it as input. In the code above it takes as input a parameter t of Type T and returns back this t .
• The lambda defining funcEmpToString is - (Employee e)-> {return e.getName();} . It takes as input an Employee object and returns his\her name, which is a String value, as output.
• The list of employees is passed to method convertEmpListToNamesList() along with the Function object funcEmpToString ;
• The method convertEmpListToNamesList() iterates over all the employees in the employee list, applies the function funcEmpToString to each of the Employee objects, getting back the employee names in String format, which it puts in a employee name list and sends it back to the main() method.
• On printing the employee name list we get the names of all the employees as required.
• Function instance funcEmpToString maps\converts an Employee object to a String of his\her name.
• Function instance initialFunction maps\converts a String to its initial or first letter.
• Default method andThen() is used to combine initialFunction with funcEmpToString . What the combined method does is that it first maps an Employee to his\her name and then takes out the first letter from the name as a String value. This combined function is passed as Function parameter to convertEmpListToNamesList() method along with the employee list.
• When the convertEmpListToNamesList() applies the combined function to each of the Employee objects, then the result is a String list first letters of names of each employee.
• This is the required output i.e. T H E N D
• Function instance funcEmpToString maps\converts an Employee object to a String value of his\her name.
• Function instance funcEmpFirstName maps\converts the name inside an Employee object to the first name using the substring method of String .
• Default method compose() is used to combine funcEmpFirstName with funcEmpToStringString . What the combined method does is that it first converts the name of an Employee into just his\her first name returning the same Employee object back with the changed value of name . It then converts\maps the Employee object to just its name as a String .This combined function is passed as Function<Employee, String> parameter to convertEmpListToNamesList() method along with the employee list.
• When the convertEmpListToNamesList() applies the combined function to each of the Employee objects, then the result is the list of first names of each employee.
• This is the required output i.e. Tom Harry Ethan Nancy Deborah
• Employee list is passed to the method applyIdentityToEmpList() along with an instance of Function.identity() . The parameter of applyIdentityToEmpList() which takes Function.identity() value is nothing but Function<Employee, Employee> i.e. an equivalent of a Function which takes Employee as input and gives back (the same) Employee as output.
• Method applyIdentityToEmpList() takes the input employee list, iterates through it, applies the identity() function to each employee in the list and returns back the list of employees obtained as a result of applying the identity() function.
• As we now know, the identity function does nothing , it just returns back the object it receives as input. So, what we get back is the same employee list which we passed to the applyIdentityToEmpList() method! And the same i.e. original employee list is printed as output!!
• This is how the static method Function.identity() works.

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The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available. See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases. See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.

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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Java Assignment Operators

Java programming tutorial index.

The Java Assignment Operators are used when you want to assign a value to the expression. The assignment operator denoted by the single equal sign = .

In a Java assignment statement, any expression can be on the right side and the left side must be a variable name. For example, this does not mean that "a" is equal to "b", instead, it means assigning the value of 'b' to 'a'. It is as follows:

Java also has the facility of chain assignment operators, where we can specify a single value for multiple variables.

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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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Example 1: Java Methods

In the above example, we have created a method named addNumbers() . The method takes two parameters a and b . Notice the line,

Here, we have called the method by passing two arguments num1 and num2 . Since the method is returning some value, we have stored the value in the result variable.

Note : The method is not static. Hence, we are calling the method using the object of the class.

• Java Method Return Type

A Java method may or may not return a value to the function call. We use the return statement to return any value. For example,

Here, we are returning the variable sum . Since the return type of the function is int . The sum variable should be of int type. Otherwise, it will generate an error.

Example 2: Method Return Type

In the above program, we have created a method named square() . The method takes a number as its parameter and returns the square of the number.

Here, we have mentioned the return type of the method as int . Hence, the method should always return an integer value.

Note : If the method does not return any value, we use the void keyword as the return type of the method. For example,

Method Parameters in Java

A method parameter is a value accepted by the method. As mentioned earlier, a method can also have any number of parameters. For example,

If a method is created with parameters, we need to pass the corresponding values while calling the method. For example,

Example 3: Method Parameters

Here, the parameter of the method is int . Hence, if we pass any other data type instead of int , the compiler will throw an error. It is because Java is a strongly typed language.

Note : The argument 24 passed to the display2() method during the method call is called the actual argument.

The parameter num accepted by the method definition is known as a formal argument. We need to specify the type of formal arguments. And, the type of actual arguments and formal arguments should always match.

• Standard Library Methods

The standard library methods are built-in methods in Java that are readily available for use. These standard libraries come along with the Java Class Library (JCL) in a Java archive (*.jar) file with JVM and JRE.

• print() is a method of java.io.PrintSteam . The print("...") method prints the string inside quotation marks.
• sqrt() is a method of Math class. It returns the square root of a number.

Here's a working example:

Example 4: Java Standard Library Method

To learn more about standard library methods, visit Java Library Methods .

What are the advantages of using methods?

1. The main advantage is code reusability . We can write a method once, and use it multiple times. We do not have to rewrite the entire code each time. Think of it as, "write once, reuse multiple times".

Example 5: Java Method for Code Reusability

In the above program, we have created the method named getSquare() to calculate the square of a number. Here, the method is used to calculate the square of numbers less than 6 .

Hence, the same method is used again and again.

2. Methods make code more readable and easier to debug. Here, the getSquare() method keeps the code to compute the square in a block. Hence, makes it more readable.

Table of Contents

• Calling a Java Method
• Method Parameters
• Advantages of Java Methods

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A method is a block of code which only runs when it is called.

You can pass data, known as parameters, into a method.

Methods are used to perform certain actions, and they are also known as functions .

Why use methods? To reuse code: define the code once, and use it many times.

Create a Method

A method must be declared within a class. It is defined with the name of the method, followed by parentheses () . Java provides some pre-defined methods, such as System.out.println() , but you can also create your own methods to perform certain actions:

Create a method inside Main:

Example Explained

• myMethod() is the name of the method
• static means that the method belongs to the Main class and not an object of the Main class. You will learn more about objects and how to access methods through objects later in this tutorial.
• void means that this method does not have a return value. You will learn more about return values later in this chapter

Call a Method

To call a method in Java, write the method's name followed by two parentheses () and a semicolon ;

In the following example, myMethod() is used to print a text (the action), when it is called:

Inside main , call the myMethod() method:

Try it Yourself »

A method can also be called multiple times:

In the next chapter, Method Parameters , you will learn how to pass data (parameters) into a method.

Test Yourself With Exercises

Insert the missing part to call myMethod from main .

Start the Exercise

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• ❯ Java Tutorial

Java Subtraction Assignment (-=) Operator

Java subtraction assignment.

In Java, Subtraction Assignment Operator is used to find the difference of the value (right operand) from this variable (left operand) and assign the result back to this variable (left operand). In this tutorial, we will learn how to use Subtraction Assignment operator in Java, with examples.

The syntax to subtract a value of 2 from variable x and assign the result to x using Subtraction Assignment Operator is

In the following example, we take a variable x with an initial value of 5 , subtract a value of 2 from x and assign the result to x , using Subtraction Assignment Operator.

In this Java Tutorial , we learned about Subtraction Assignment Operator in Java, with examples.

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