Decision Statements in Java

The if-else statement

The if-else control statement allows the execution of instructions in the if block only if it satisfies a given condition. If it does not fulfil the condition, then the code present in the else block is executed. The use of this control statement ensures the execution of either the if block or the else block compulsorily.

Syntax:

if(condition)
{
  Statements of if block
}
else
{
   Statements of else block
}

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Note: If there are no brackets to include the statements of a block, only the first line after the if/else control statement is executed as part of it.

Here is an example of the if-else statement in Java.

public class Main 
{
   public static void main(String args[])
  {
      int i = 20;
      if (i < 15)
      {
        int difference = 15-i;
        System.out.println("The value is less than 15 by " + difference);
      }
      else
      {
        int difference = i-15;
        System.out.println("The value is greater than 15 by " + difference);
      }
      System.out.println("End");
  }
}

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Output:

The value is greater than 15 by 5
End

Short-hand notation

The ternary operator ?: can be used as a short-hand of the if-else control statement.

Syntax:

(condition)?result1:result2;

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If the condition is true, then result1 is the answer. Otherwise, result2 is the answer.

public class Main 
{
  public static void main(String args[])
  {
      int i = 10;
      String Answer = (i%2 == 0)?"Even":"Odd";
      System.out.println(Answer);
  }
}

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Output:

Even

Also see, Swap Function in Java

The else-if ladder

The else-if ladder allows the execution of the instructions in the if block or the consecutive else-if block only if it satisfies their given condition. The else block is executed if none of the conditions are met. The else-if control statements are used when multiple cases are possible for a given situation, but a single and final output is required.

Syntax:

if(condition1)
{
   Statements
}
else if(condition2)
{
  Statements
}
else if(condition3)
{
  Statements
}
...
else
{
  Statements
}

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Here is an example of the else-if ladder in Java.

public class Main 
{
   public static void main(String args[])
  {
      int i = 15;
      if (i < 15)
        System.out.println("The value is less than 15 by " + (15-i));
      else if (i > 15)
        System.out.println("The value is greater than 15 by = " + (i-15));
      else
        System.out.println("The value is equal to 15");
   }
}

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Output:

The value is equal to 15

You can also check out Has-A Relationship in Java here.

Must Read Conditional Statements in Java

Related Article What are Loops in Java

FAQs

1. What are logical operators?
   && (AND) - It returns true only if both its operands are true.
   || (OR) - It returns true if at least one of its operands is true.
   ! (NOT) - It returns true if its operand is false and vice versa.
    
2. What is the main difference between the else if ladder and switch-case statements?
   The else if ladder executes a set of statements based on boolean values while a switch case statement executes a block of statements based on the equality of a variable to a case.

Key Takeaways

Decisional control statements have a lot of practical applications and are extremely useful to programmers when they come across situations where a constraint is to be added. This blog has discussed the list of control statements in Java and a few examples to understand them better.

Related Links:

Conditional statements in C++

Conditional Statements in Python

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