Decision making Statements

The Java if statement is used to test the condition. It checks boolean condition: true or false. There are various types of if statement in java.

• if statement
• if-else statement
• if-else-if ladder
• nested if statement

Java if Statement

• Based on some condition if we want to execute some set of statements then we need to use if condition in java.
• We need to keep all the required statements inside if block .
• If the condition is true then control executes the whole block otherwise it skips the if block of statements.

The structure of the “if” statement in Java looks like this:

Syntax :

if (condition) {
  // execute this code
}

Java example program on if control statement:

public class IfExample{
	public static void main(String[] args) {
		int age = 3;
		System.out.println("Shivani is " + age + " years old");
		if (age < 4) {
			System.out.println("Shivani is a baby");
		}
	}
}

Output :

Shivani is 3 years old
Shivani is a baby

Output Detail : In the example above we check if the age is lower than 4. As the age is set to be 3, the boolean condition age < 4 is true and as result we print “Shivani is a baby”. If we change the age to any value greater than 3 the code in the block want execute anymore and “Shivani is a baby” is not printed.

Java IF-else Statement

• If the condition is true then control executes the whole block otherwise it skips the if block of statements
• if condition is false  if we need to execute another set of statement we can write another if and keep all the statements in that block.
• instead of checking multiple times we can simply use else block .

The structure of the “if-else” statement in Java looks like this:

Syntax :

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

Java example program on if-else control statement:

public class IfElseExample{
	public static void main(String[] args) {
		int age = 15;
		System.out.println("Shivani is " + age + " years old");
		if (age < 4) {
			System.out.println("Shivani is a baby");
		}else{
			System.out.println("Shivani is not a baby may be adult");
        }
	}
}

Output

Shivani is 15 years old
Shivani is not a baby may be adult

Output Detail : In the example above we check if the age is lower than 4. As the age is set to be 15, the boolean condition age < 4 is true and as result we print “Shivani is a baby”. If we change the age to any value greater than 4 the code in the block want execute anymore and “Shivani is not a baby may be adult” is printed.

Java if-else-if ladder Statement

• instead of checking multiple times we can simply use else block .
• In some cases we may get requirement with multiple conditions in such cases we need to use if else ladder.(if -else-if-else if -else...)

The structure of the “if-else-if ladder” statement in Java looks like this:

Syntax :

if(condition1){  
//code to be executed if condition1 is true  
}else if(condition2){  
//code to be executed if condition2 is true  
}  
else if(condition3){  
//code to be executed if condition3 is true  
}  
else if(condition4){  
//code to be executed if condition4 is true  
}   
...  
else{  
//code to be executed if all the conditions are false  
}  

Java example program on if-else-if ladder control statement:

public class IfElseIfLedder{
	public static void main(String[] args) {
		int age = 20;
		System.out.println("Shivani is " + age + " years old");
		if (age < 4) {
			System.out.println("Shivani is a baby");
		} else if (age >= 4 && age < 14) {
			System.out.println("Shivani is a child");
		} else if (age >= 14 && age < 18) {
			System.out.println("Shivani is a teenager");
		} else if (age >= 18 && age < 68) {
			System.out.println("Shivani is adult");
		} else {
			System.out.println("Shivani is an old women");
		}
	}
}

Output :

Shivani is 20 years old
Shivani is adult