Decision Statements in Java

In this article you will learn about the decision making statements and its uses

Decision making statements in Java

As the name says, decision making statements are used to make decisions in critical situation in executing a program. It helps to write decision driven statements and execute a particular block of code based on the required conditions. Java supports the following decision making statements.

• if statement
• if-else statement
• if-else-if ladder
• nested if statement
• switch statement
• conditional operator

Let’s discuss them in detail

if statement

The if statement in Java is the simplest decision-making statement. The Java if statement is used to test the condition. In simple, if a certain condition is met, then it executes a specific block of code. Otherwise, executes another block code.

Syntax

if(condition) 
{
   // Statements to execute if the condition is true
}

Sample program using If.. statement in Java

Input

public class Main{  
public static void main(String[] args) {  
    
    int age=20;  
    if(age>18){  
        System.out.print("Age is greater than 18, checked using if statement.");  
    }  
}  
}

Output

Age is greater than 18, checked using if statement.

if...else statement

The if-else statement in Java like the if statement, it also tests the condition. It executes the ‘if block of codes’ if the condition is true otherwise ‘else block of codes’ will be executed. In simple, the else statement executes when the Boolean expression is false.

Syntax:

if (condition)
{
    // Executes this block if the condition is true
}
else
{
    // Executes this block if the condition is false
    
}

Sample program using if…else statement in Java

Input

public class Main {
  public static void main(String[] args) {
    int number = 57;
    if (number > 10) {
      System.out.println("The number is greater than 10.");
    }
        else {
      System.out.println("The number is lesser than 10.");
    }
  }
}

Output

The number is greater than 10.

Nestedif statement

Java allows us to use multiple if or if else statements inside another if statements. But on a condition, the inner if block condition executes only when outer if block condition is true.

Syntax

if(condition){    
     //code to be executed if the condition is met
          if(condition){  
             //code to be executed if the condition is met
    }    
}

Sample program using Nestedif statement in Java

Input

public class Main {      
public static void main(String[] args) {      
    int age=21;    
    int weight=58;      
        if(age>=18){      
        if(weight>60){    
            System.out.println("You are eligible to donate blood");    
        } else{  
            System.out.println("Sorry, you are not eligible to donate blood");    
        }  
    } else{  
      System.out.println("You must be of legal age ");  
    }  
}  }
  }

Output

Sorry, you are not eligible to donate blood

Switch statement in Java

A switch statement allows a variable to be tested for equality against a list of values. The switch statement is a multi-way case statement. The switch statement allows us to execute a particular block of code based on the condition,among many alternatives(cases). The switch statement works with almost all data types byte, short, int, long, enum types and String. With the latest version of Java, you can use strings in the switch statement.

Syntax

switch (expression) {
  case value1:
    // code to be executed if expression is equal to value1
break;
  
  case value2:
    // code to be executed if expression is equal to value2
    
    break;
  
  ...
  ...
  
  default:
    // default statements
  }

Sample program using switch statements in Java

Input

int day = 5;
switch (day) {
  case 1:
    System.out.println("Monday");
    break;
  case 2:
    System.out.println("Tuesday");
    break;
  case 3:
    System.out.println("Wednesday");
    break;
  case 4:
    System.out.println("Thursday");
    break;
  case 5:
    System.out.println("Friday");
    break;
  case 6:
    System.out.println("Saturday");
    break;
  case 7:
    System.out.println("Sunday");
    break;
}

Output

Friday

Conditional Operator ( ? : )

Conditional operator is also known as the ternary operator. This operator consists of three operands and is used to evaluate Boolean expressions.

Syntax

variable x = (expression) ? value if true : value if false

Sample program for a conditional operator in Java

Input

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

    int februaryDays = 29;
    String result;

        result = (februaryDays == 28) ? "Not a leap year" : "Leap year";
    System.out.println(result);
  }
}

Output

Leap year