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Java if-else ​

Java supports the usual logical conditions from mathematics:

  • Less than: a < b
  • Less than or equal to: a <= b
  • Greater than: a > b
  • Greater than or equal to: a >= b
  • Equal to a == b
  • Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

Java has the following conditional statements:

  • Use if to specify a block of code to be executed, if a specified condition is true

  • Use else to specify a block of code to be executed, if the same condition is false

  • Use else if to specify a new condition to test, if the first condition is false

  • Use switch to specify many alternative blocks of code to be executed

The if Statement ​

Use the if statement to specify a block of Java code to be executed if a condition is true.

Syntax

java
if (condition) {
  // block of code to be executed if the condition is true
}
if (condition) {
  // block of code to be executed if the condition is true
}

Example

java
if (20 > 18) {
  System.out.println("20 is greater than 18");
}
if (20 > 18) {
  System.out.println("20 is greater than 18");
}

The else Statement ​

Use the else statement to specify a block of code to be executed if the condition is false.

Syntax

java
if (condition) {
  // block of code to be executed if the condition is true
} else {
  // block of code to be executed if the condition is false
}
if (condition) {
  // block of code to be executed if the condition is true
} else {
  // block of code to be executed if the condition is false
}

Example

java
int time = 20;
if (time < 18) {
  System.out.println("Good day.");
} else {
  System.out.println("Good evening.");
}
int time = 20;
if (time < 18) {
  System.out.println("Good day.");
} else {
  System.out.println("Good evening.");
}

The else if Statement ​

Use the else if statement to specify a new condition if the first condition is false.

Syntax

java
if (condition1) {
  // block of code to be executed if condition1 is true
} else if (condition2) {
  // block of code to be executed if the condition1 is false and condition2 is true
} else {
  // block of code to be executed if the condition1 is false and condition2 is false
}
if (condition1) {
  // block of code to be executed if condition1 is true
} else if (condition2) {
  // block of code to be executed if the condition1 is false and condition2 is true
} else {
  // block of code to be executed if the condition1 is false and condition2 is false
}

Example

java
int time = 22;  
if (time < 10) {
  System.out.println("Good morning.");
} else if (time < 20) {
  System.out.println("Good day.");
} else {
  System.out.println("Good evening.");
}
int time = 22;  
if (time < 10) {
  System.out.println("Good morning.");
} else if (time < 20) {
  System.out.println("Good day.");
} else {
  System.out.println("Good evening.");
}

Short Hand If...Else (Ternary Operator) ​

There is also a short-hand if else, which is known as the ternary operator because it consists of three operands. It can be used to replace multiple lines of code with a single line. It is often used to replace simple if else statements:

Syntax

java
variable = (condition) ? expressionTrue :  expressionFalse;
variable = (condition) ? expressionTrue :  expressionFalse;

Example

java
int time = 20;
String result = (time < 18) ? "Good day." : "Good evening.";
System.out.println(result);
int time = 20;
String result = (time < 18) ? "Good day." : "Good evening.";
System.out.println(result);