If else statement

The if statement is a conditional branch statement. Here is the general form of the if-else statement:

 
if (condition) 
   statement1; 
else 
   statement2;

The else clause is optional.

Each statement may be a single statement or a compound statement enclosed in curly braces (a block).

The condition is any expression that returns a boolean value.

Only one statement can appear directly after the if or the else. To include more statements, you'll need to create a block, as in this fragment:

  
public class Main {
  public static void main(String[] argv) {
    int i = 1;

    if (i > 0) {
      System.out.println("Here");
      i -= 1;

    } else
      System.out.println("There");
  }
}

The output:


Here

It is convenient to include the curly braces when using the if statement, even when there is only one statement in each clause.

Nested if statements

A nested if is an if statement inside another another if statement or else.

  
public class Main {
  public static void main(String[] argv) {
    int i = 10;
    int j = 4;
    int k = 200;
    int a = 3;
    int b = 5;
    int c = 0;
    int d =0;
    if (i == 10) {
      if (j < 20){
        a = b;
      }
      if (k > 100){
        c = d;
      }
      else{
        a = c;
      }
    } else{
      a = d;
    }
    System.out.println("a = " + a);
    System.out.println("b = " + b);
    System.out.println("c = " + c);
    System.out.println("d = " + d);
    
  }
}

The output:


a = 5
b = 5
c = 0
d = 0

The if-else-if Ladder

It looks like this:

 
if(condition) 
   statement; 
else if(condition) 
   statement; 
else if(condition) 
   statement; 
. 
.
else 
   statement;

Here is a program that uses an if-else-if ladder.

 
public class Main {
  public static void main(String args[]) {
    int month = 4;
    String value;
    if (month == 1 )
      value = "A";
    else if (month == 2)
      value = "B";
    else if (month == 3)
      value = "C";
    else if (month == 4)
      value = "D";
    else
      value = "Error";

    System.out.println("value = " + value);
  }
}

Here is the output produced by the program:


value = D

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