Java Operator Precedence

Operator Precedence in Java

In Java, when you write a complex expression involving multiple operators, the order in which those operators are evaluated is governed by a set of rules called operator precedence.

If you've ever wondered why 2 + 3 * 4 doesn't equal 20, then operator precedence is the reason.

What is Operator Precedence?

Operator precedence determines the order in which different operators in an expression are evaluated. For instance, multiplication has higher precedence than addition, so it is performed first.

What is Associativity?

When two operators have the same precedence, associativity determines the direction of evaluation. It can be either:

• Left-to-right: Most binary operators (e.g., +, -, *, /)
• Right-to-left: Unary, assignment, and ternary operators

Java Operator Precedence Table

Here’s a simplified view of Java operators from highest to lowest precedence:

Basic Example: Precedence in Action

public class Main {
  public static void main(String[] args) {
    int result = 10 + 2 * 3;
    System.out.println("Result: " + result);
  }
}

Result: 16

Explanation: 2 * 3 is evaluated first (due to higher precedence), and then 10 + 6 is evaluated.

Using Parentheses to Control Precedence

public class Main {
  public static void main(String[] args) {
    int result = (10 + 2) * 3;
    System.out.println("Result: " + result);
  }
}

Result: 36

Explanation: By wrapping 10 + 2 in parentheses, we change the natural order of evaluation.

Associativity Example

public class Main {
  public static void main(String[] args) {
    int a = 20, b = 10, c = 5;
    int result = a - b - c;
    System.out.println("Result: " + result);
  }
}

Result: 5

Explanation: Since - has left-to-right associativity, evaluation happens like (20 - 10) - 5.

Assignment Associativity (Right to Left)

public class Main {
  public static void main(String[] args) {
    int a, b, c;
    a = b = c = 100;
    System.out.println(a + " " + b + " " + c);
  }
}

100 100 100

Explanation: Assignment operators are evaluated from right to left: c = 100, then b = c, then a = b.

Common Pitfall Example

public class Main {
  public static void main(String[] args) {
    boolean result = true || false && false;
    System.out.println(result);
  }
}

true

Explanation: && has higher precedence than ||, so false && false is evaluated first (which is false), then true || false becomes true.

Why Precedence Matters

Even a minor mistake in understanding precedence can lead to incorrect logic and subtle bugs. Always use parentheses to make your intent clear, especially in complex conditions or calculations.

Best Practices

• Use parentheses generously for clarity, not just correctness.
• Always know your associativity when chaining operators.
• Don’t rely solely on precedence—aim for readable, maintainable code.