JavaCore java

If else in Java

Conditional Statements

Decision-making statements in Java.
Used to control program flow based on conditions.

General Form:

if (condition) {
    // executes if condition is true
} else {
    // executes if condition is false
}

Flowchart Representation

        [Condition?]
           /   \
        True    False
        /          \
 [Execute Block1]  [Execute Block2]

Example – Car Speed

If speed is greater than allowed → decrease
If speed is less than allowed → increase
If equal → stop / maintain speed

Example 1 – Basic If

public class Demo {
    public static void main(String[] args) {
        int x = 18;
        if (x > 10) {
            System.out.println("Hello");
        }
    }
}

If condition is true → block executes.
If condition is false → block is skipped.

Example 2 – If with Else

int x = 8;
if (x > 10 && x <= 20) {   // 11 - 20
    System.out.println("Hello");
} else {
    System.out.println("Bye");
}

Note:

if can be used alone.
else cannot be used without if.

Example 3 – Comparing Two Numbers

int x = 5;
int y = 7;

if (x > y) {
    System.out.println(x);
} else {
    System.out.println(y);
}

👉 Output: 7

Example 4 – Braces are Important

if (x > y)
    System.out.println(x);
    System.out.println("Thank you"); // Always executes, not part of if
else
    System.out.println(y); // ❌ Error: 'else' without 'if'

✅ Correct way:

if (x > y) {
    System.out.println(x);
    System.out.println("Thank you");
} else {
    System.out.println(y);
}

Key Notes

Java does not depend on indentation (unlike Python).
Always use {} if more than one statement in a block.
Helps avoid logical errors.

Relational Operator in Java

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Conditional Statements General Form:Flowchart Representation Example – Car Speed Example 1 – Basic If Example 2 – If with Else Note:Example 3 – Comparing Two Numbers Example 4 – Braces are Important Key Notes