Java if, if-else, switch, break, continue, jump

Java if, if-else, switch, break, continue, jump
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If-else: The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it will not. But if we want to do something else Here comes the else statement. We can use the else statement with if statement to execute a block of code when the condition is false.

Syntax:

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

Example:

// Java program to illustrate if-else statement class IfElseDemo {     public static void main(String args[])     {         int i = 10;            if (i < 15)             System.out.println("i is smaller than 15");         else             System.out.println("i is greater than 15");     } }

Output:

i is smaller than 15

nested-if: A nested if is an if statement that is the target of another if or else. Nested if statements mean an if statement inside an if statement. Yes, Java allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement.
Syntax:

if (condition1) 
{
   // Executes when condition1 is true
   if (condition2) 
   {
      // Executes when condition2 is true
   }
}

Example:

// Java program to illustrate nested-if statement class NestedIfDemo {     public static void main(String args[])     {         int i = 10;            if (i == 10)         {             // First if statement             if (i < 15)                 System.out.println("i is smaller than 15");                // Nested - if statement             // Will only be executed if statement above             // it is true             if (i < 12)                 System.out.println("i is smaller than 12 too");             else                 System.out.println("i is greater than 15");         }     } }

Output:

i is smaller than 15
i is smaller than 12 too

switch-case:- The switch statement is a multiway branch statement. It provides an easy way to dispatch execution to different parts of code based on the value of the expression.
Syntax:

switch (expression)
{
  case value1:
    statement1;
    break;
  case value2:
    statement2;
    break;
  .
  .
  case valueN:
    statementN;
    break;
  default:
    statementDefault;
}

Example:

// Java program to illustrate switch-case class SwitchCaseDemo {     public static void main(String args[])     {         int i = 9;         switch (i)         {         case 0:             System.out.println("i is zero.");             break;         case 1:             System.out.println("i is one.");             break;         case 2:             System.out.println("i is two.");             break;         default:             System.out.println("i is greater than 2.");         }     } }

• Output:

  i is greater than 2.

jump: Java supports three jump statement: break, continue and return. These three statements transfer control to other part of the program.

1. Break: In Java, the break is majorly used for:
   • Terminate a sequence in a switch statement 
   • To exit a loop.
   • Used as a “civilized” form of goto.

Example:

// Java program to illustrate using // break to exit a loop class BreakLoopDemo {     public static void main(String args[])     {         // Initially loop is set to run from 0-9         for (int i = 0; i < 10; i++)         {             // terminate loop when i is 5.             if (i == 5)                 break;                System.out.println("i: " + i);         }         System.out.println("Loop complete.");     } }

Output:

i: 0
i: 1
i: 2
i: 3
i: 4
Loop complete.

Example:

// Java program to illustrate using break with goto class BreakLabelDemo {     public static void main(String args[])     {         boolean t = true;            // label first         first:         {             // Illegal statement here as label second is not             // introduced yet break second;             second:             {                 third:                 {                     // Before break                     System.out.println("Before the break statement");                        // break will take the control out of                     // second label                     if (t)                         break second;                     System.out.println("This won't execute.");                 }                 System.out.println("This won't execute.");             } // Third block             System.out.println("This is after second block.");         }     } }

Output:

Before the break.
This is after second block.

Continue: Sometimes it is useful to force an early iteration of a loop. That is, you might want to continue running the loop but stop processing the remainder of the code in its body for this particular iteration. This is, in effect, a goto just past the body of the loop, to the loop’s end. The continue statement performs such an action.

Example:

// Java program to illustrate using // continue in an if statement class ContinueDemo {     public static void main(String args[])     {         for (int i = 0; i < 10; i++)         {             // If the number is even             // skip and continue             if (i%2 == 0)                 continue;                // If number is odd, print it             System.out.print(i + " ");         }     } }

Output:

1 3 5 7 9 

Return: The return statement is used to explicitly return from a method. That is, it causes a program control to transfer back to the caller of the method.
Example:

// Java program to illustrate using return class Return {     public static void main(String args[])     {         boolean t = true;         System.out.println("Before the return.");                if (t)             return;            // Compiler will bypass every statement          // after return         System.out.println("This won't execute.");     } }

Output:

Before the return.