else_Keyword

Java if,if else,nested if, if else if Statement with Examples

In this quick article, we will learn Java if statement and different types of if statement in Java, which is used to test the condition. It checks boolean condition: true or false.
There are various types of if statement in java.

• if Statement
• nested if Statement
• if-else Statement
• if-else-if Statement
• Java if Statement
  The Java if statement tests the condition. It executes the if block if a condition is true.

Syntax

if(condition){  
//code to be executed  
}

Here, if statement may be a single statement or a compound statement enclosed in curly braces (that is, a block).
The statements get executed only when the given condition is true. If the condition is false then the statements inside if statement body is completely ignored.

Java if Statement Example

package net.javaguides.corejava.controlstatements.ifelse;

public class IfStatementExample {
    public static void main(String[] args) {
        int x, y;
        x = 10;
        y = 20;
        if (x < y) {
            System.out.println("x is less than y");
        }
        x = x * 2;
        if (x == y) {
            System.out.println("x now equal to y");
        }
        x = x * 2;
        if (x > y) {
            System.out.println("x now greater than y");
        }
        // this won't display anything
        if (x == y)
            System.out.println("you won't see this");
    }
}

Output:

x is less than y
x now equal to y
x now greater than y

Java Nested if Statement

When there is an if statement inside another if statement then it is called the nested if statement.
Syntex

if(condition_1) {
   Statement1(s);

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

Java Nested if Statement example

package net.javaguides.corejava.controlstatements.ifelse;

public class NetstedIfStatementExample {
    public static void main(String[] args) {
        int num = 50;
        if (num < 100) {
            System.out.println("number is less than 100");
            if (num == 50) {
                System.out.println("number equal to 50");
                if (num > 40) {
                    System.out.println("number is greater than 40");
                }
            }
        }
    }
}

Output:

number is less than 100
number equal to 50
number is greater than 40

Java if-else Statement

The Java if-else statement also tests the condition. It executes the if block if a condition is true otherwise else block, is executed.

Syntex

if(condition){  
     statement 1; //code if condition is true  
}else{  
     statement 2; //code if condition is false  
}  

Here, each statement may be a single statement or a compound statement enclosed in curly braces (that is, a block). The condition is an expression that returns a boolean value.
The if works like this: If the condition is true, then statement1 is executed. Otherwise, statement2 (if it exists) is executed.

Java if-else Statement Example

The following program, IfElseDemo, assigns a grade based on the value of a test score: an A for a score of 90% or above, a B for a score of 80% or above, and so on.

package net.javaguides.corejava.controlstatements.ifelse;

public class IfElseDemo {
    public static void main(String[] args) {

        int testscore = 76;
        char grade;

        if (testscore >= 90) {
            grade = 'A';
        } else if (testscore >= 80) {
            grade = 'B';
        } else if (testscore >= 70) {
            grade = 'C';
        } else if (testscore >= 60) {
            grade = 'D';
        } else {
            grade = 'F';
        }
        System.out.println("Grade = " + grade);
    }
}

Output:

Grade = C

Note that the value of test score can satisfy more than one expression in the compound statement: 76 >= 70 and 76 >= 60. However, once a condition is satisfied, the appropriate statements are executed (grade = ‘C’? and the remaining conditions are not evaluated.

Java if-else-if Statement

A common programming construct that is based upon a sequence of nested ifs is the if-else-if ladder.
Syntex

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{  
//code to be executed if all the conditions are false  
}  

The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed.
If none of the conditions is true, then the final else statement will be executed. The final else acts as a default condition; that is, if all other conditional tests fail, then the last else statement is performed. If there is no final else and all other conditions are false, then no action will take place.
Java if-else-if Statement Example
Here is a program that uses an if-else-if ladder to determine which season a particular month is in.

package net.javaguides.corejava.controlstatements.ifelse;

public class IfElseIfStatementExample {
    public static void main(String args[]) {
        int month = 4; // April
        String season;
        if (month == 12 || month == 1 || month == 2)
            season = "Winter";
        else if (month == 3 || month == 4 || month == 5)
            season = "Spring";
        else if (month == 6 || month == 7 || month == 8)
            season = "Summer";
        else if (month == 9 || month == 10 || month == 11)
            season = "Autumn";
        else
            season = "Bogus Month";
        System.out.println("April is in the " + season + ".");
    }
}

Output:

April is in the Spring.

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