JAVA

Operators & Expressions

Variables allow us to store data, but storing data alone is not very useful. In real-world programs, we often need to perform calculations, compare values, and make decisions based on data. For example, an e-commerce application may need to calculate a product's total price, while a banking application may need to check whether an account has sufficient balance.

To perform such operations, Java provides operators. Operators are special symbols that perform actions on values and variables. The result produced by combining values, variables, and operators is known as an expression.

In this chapter, you will learn how to perform calculations, compare values, update variables, and combine conditions using Java operators.

What is an Operator?

An operator is a symbol that tells Java to perform a specific operation.

Example:

int sum = 10 + 20;

Here, + is an operator that adds two numbers.

The result is:

30

What is an Expression?

An expression is a combination of values, variables, and operators that produces a result.

Example:

10 + 20

This expression evaluates to:

30

Another example:

age + 5

If age is 18, the expression evaluates to:

23

Arithmetic Operators

Arithmetic operators are used for mathematical calculations.

Example:

int a = 10;
int b = 3;

System.out.println(a + b);
System.out.println(a - b);
System.out.println(a * b);
System.out.println(a / b);
System.out.println(a % b);

Output:

13
7
30
3
1

Assignment Operator

The assignment operator is used to assign a value to a variable.

int age = 18;

Here, the = operator assigns the value 18 to the variable age.

You can also update a variable:

age = 20;

Now the value of age becomes 20.

Comparison Operators

Comparison operators compare two values and return either true or false.

Example:

int age = 18;

System.out.println(age >= 18);

Output:

true

Logical Operators

Logical operators are used to combine multiple conditions.

Example:

boolean hasTicket = true;
boolean hasId = true;

System.out.println(hasTicket && hasId);

Output:

true

The result is true because both conditions are true.

Increment and Decrement Operators

These operators increase or decrease a variable's value by one.

Increment:

int count = 5;

count++;

Value of count becomes:

6

Decrement:

int count = 5;

count--;

Value of count becomes:

4

Example Program

public class Main {
    public static void main(String[] args) {

        int price = 500;
        int quantity = 2;

        int total = price * quantity;

        System.out.println(total);
    }
}

Output:

1000

In this program:

• price stores the price of one product.
• quantity stores the number of products.
• * multiplies the two values.
• The result is stored in total.
• System.out.println() displays the result.

Understanding the Modulus Operator

The modulus operator (%) returns the remainder after division.

Example:

System.out.println(10 % 3);

Output:

1

Because:

10 ÷ 3 = 3 remainder 1

This operator is commonly used to check whether a number is even or odd.

Example:

System.out.println(8 % 2);

Output:

0

Since the remainder is 0, the number is even.

Common Mistakes

Using = Instead of ==

Wrong:

if(age = 18)

Correct:

if(age == 18)

= assigns a value.

== compares values.

Expecting Decimal Results from Integer Division

System.out.println(10 / 3);

Output:

3

Both values are integers, so Java returns an integer result.

To get decimals:

System.out.println(10.0 / 3);

Output:

3.3333333333333335

Key Takeaways

• Operators perform actions on values and variables.
• Expressions produce a result.
• Arithmetic operators are used for calculations.
• Comparison operators return true or false.
• Logical operators combine multiple conditions.
• Increment and decrement operators change a value by one.
• Operators are fundamental to calculations, conditions, and loops throughout Java programs.