If-else statements, syntax and examples in java

When we have to execute a set of statements based on a condition, we need control flow statements. For example, if a number is greater than zero then we want to print “positive number” but if it is less than zero then we want to print “negative number”. In this case we have 2 print statements in the program but only one print statement is executed based on the input value.

In this notes, we will see how programs are written in Java based on a particular condition using control statements. In this notes we will see 4 types of control statements that you can use in Java program depending on the requirement, in this tutorial we will look at the following statements in detail.

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

if statement

The if statement checks the condition as shown below.

if (condition) {
statement(s);
}

If the condition is true then the statements are executed and if the condition is false then the statement body is completely ignored.

Examples

public class IfStatementExample {

  public static void main(String args[]){
   int num=70;
   if(num < 100){
	 /* This println statement will only execute,
	  * if the above condition is true
	  */
	 System.out.println("number is less than 100");
   }
  }
}

Output
number is less than 100

Nested if statement

When there is another if statement inside if statement then it is called nested if statement. nested if statement is written as

if(condition_1) {
Statement1(s);

if(condition_2) {
Statement2(s);
}
}

Here statement 1 will execute only if condition1 is true and statement 2 will execute only when both condition1 and condition2 are true.

Examples

public class NestedIfExample 
{
	public static void main(String args[])
	{
		int num=70;
		if(num < 100)
		{
			System.out.println("number is less than 100");
			if(num > 50)
			{
				System.out.println("number is greater than 50");
			}
		}
	}
}

Output

number is less than 100
number is greater than 50

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if-else statement

The if-else statement is written like this.

if(condition) 
{
	Statement(s);
}
else 
{
	Statement(s);
}

If the condition is true then the statements inside “if” will execute and if the condition is false then the statements inside “else” are executed.

Examples

public class IfElseExample{
	public static void main(String args[]){
		int num=120;
		if(num < 50){
			System.out.println("num is less than 50");
		}
		else {
		System.out.println("num is greater than or equal 50");
		}
	}
}

Output
num is greater than or equal 50

if-else-if statement

The if-else-if statement is used to test multiple conditions. In this statement we have only one “if” and only one “else” although we can also have multiple “else if” It is also known as if-else-if ladder. The if-else-if statement is written as:

if(condition_1) {
/*if condition_1 is true execute this*/
statement(s);
}
else if(condition_2) {
/* execute this if condition_1 is not met and
* condition_2 is met
*/
statement(s);
}
else if(condition_3) {
/* execute this if condition_1 & condition_2 are
* not met and condition_3 is met
*/
statement(s);
}
.
.
.
else {
/* if none of the condition is true
* then these statements gets executed
*/
statement(s);
}

note : – The most important thing to note here is that as soon as the condition is found true in the if-else-if statement then the set of statements is executed and the rest is ignored. If no condition is met, then the statements inside “else” are executed.

Examples

public class IfElseIfExample {
public static void main(String args[]){
int num=1234;
if(num <100 && num>=1) {
System.out.println("Its a two digit number");
}
else if(num <1000 && num>=100) {
System.out.println("Its a three digit number");
}
else if(num <10000 && num>=1000) {
System.out.println("Its a four digit number");
}
else if(num <100000 && num>=10000) {
System.out.println("Its a five digit number");
}
else {
System.out.println("number is not between 1 & 99999");
}
}
}

Output
Its a four digit number

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