What is if-else?

The if-else statement allows a program to choose between two blocks of code based on a condition.

It’s useful when you want to handle both possibilities of a condition.

Key Points:

• It allows execution of one of two blocks depending on the boolean condition.
• If the condition is true → if block is executed.
• If the condition is false → else block is executed.
• Only one block runs at a time — either if or else, never both.
• Conditions often involve relational (>, <, ==, etc.) or logical (&&,||, !) operators.

Syntax:

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

Flow diagram for the following examples:

Algorithm of if else

1. Starts with variable initialization
2. Checks if marks >= 50
3. Based on result:
4. if block runs: prints "Inside if block" and "Pass!"
5. or else block runs: prints "Inside else block" and "Fail!"
6. Then always prints: "Hello from outside!"
7. Ends

Example 1:

class ShikshaSanchar {
  public static void main(String[] args) {
    int marks = 45;
    if (marks >= 50) {
        System.out.println("Inside if block!");
        System.out.println("Pass!");
    } else {
        System.out.println("Inside else block!");
        System.out.println("Fail!");
    }
    System.out.println("Hello from outside!");
  }
}

Example 2:

class ShikshaSanchar {
  public static void main(String[] args) {
    int marks = 90;
    if (marks >= 50) {
        System.out.println("Inside if block!");
        System.out.println("Pass!");
    } else {
        System.out.println("Inside else block!");
        System.out.println("Fail!");
    }
    System.out.println("Hello from outside!");
  }
}

Important Points about if-else in Java:

• if-else is used to handle two alternative cases based on a condition.
• The else block must immediately follow the if block — nothing should come in between.
• You cannot use else alone — it must be attached to an if.
• Only one block executes:
  • If condition is true → if block runs.
  • If condition is false → else block runs.
• Curly braces {} are optional if the block contains only one statement.

int marks = 80;

if (marks >= 50)
  System.out.println("Pass!");
else
  System.out.println("Fail!");

• Each block contains only one statement, so curly braces are not required.
• But if you have more than one line, braces are mandatory to group the block.
• Conditions must return a boolean value (true/false).
• You can use logical operators (&&, ||, !) to combine multiple conditions in the if.

Summary: