Java Conditional Statements - if...else
An if statement contains a boolean expression and one or more statements.
Syntax
The syntax for an if statement is as follows:
if(boolean expression)
{
// Statements to be executed if the boolean expression is true
}
If the value of the boolean expression is true, the code block inside the if statement is executed; otherwise, the code following the if block is executed.
Test.java File Code:
public class Test {
public static void main(String args[]){
int x = 10;
if( x < 20 ){
System.out.print("This is the if statement");
}
}
}
The above code compiles and runs with the following result:
This is the if statement
if...else Statement
An if statement can be followed by an else statement, which executes when the boolean expression in the if statement is false.
Syntax
The syntax for if…else is as follows:
if(boolean expression){
// Executes if the boolean expression is true
}else{
// Executes if the boolean expression is false
}
Example
Test.java File Code:
public class Test {
public static void main(String args[]){
int x = 30;
if( x < 20 ){
System.out.print("This is the if statement");
}else{
System.out.print("This is the else statement");
}
}
}
The above code compiles and runs with the following result:
This is the else statement
if...else if...else Statement
An if statement can be followed by one or more else if...else statements, which can test multiple conditions.
When using if, else if, else statements, note the following:
- There can be at most one else statement, which comes after all the else if statements.
- There can be multiple else if statements before the else statement.
- Once one of the else if statements evaluates to true, the others, including the else statement, are skipped.
Syntax
The syntax for if...else is as follows:
if(boolean expression 1){
// Executes if boolean expression 1 is true
}else if(boolean expression 2){
// Executes if boolean expression 2 is true
}else if(boolean expression 3){
// Executes if boolean expression 3 is true
}else {
// Executes if none of the above boolean expressions are true
}
Example
Test.java File Code:
public class Test {
public static void main(String args[]){
int x = 30;
if( x == 10 ){
System.out.print("Value of X is 10");
}else if( x == 20 ){
System.out.print("Value of X is 20");
}else if( x == 30 ){
System.out.print("Value of X is 30");
}else{
System.out.print("This is the else statement");
}
}
}
The above code compiles and runs with the following result:
Value of X is 30
Nested if…else Statement
Using nested if…else statements is legal. This means you can use an if or else if statement inside another if or else if statement.
Syntax
The syntax for nested if…else is as follows:
if(boolean expression 1){
// Executes if boolean expression 1 is true
if(boolean expression 2){
// Executes if boolean expression 2 is true
}
}
You can nest else if...else in the same way as an if statement.
Example
Test.java File Code:
public class Test {
public static void main(String args[]){
int x = 30;
int y = 10;
if( x == 30 ){
if( y == 10 ){
System.out.print("X = 30 and Y = 10");
}
}
}
}
The above code compiles and runs with the following result:
X = 30 and Y = 10
if( x == 30 ){
if( y == 10 ){
System.out.print("X = 30 and Y = 10");
}
}
The above code compiles and runs with the following result:
X = 30 and Y = 10