Java For Loop

The for is a entry-controlled loop that provides a more short loop control structure that other loops.

For loop is the most popular looping instruction due to it's simple instruction.

Syntax

for (initialization; test-condition; increment/decrement)
{
    // body of for loop
    ....
    ....
    ....
}

Flowchart

Syntax Explanation

The execution of the for statement is performed based on following 3 steps.

1. Initialization
2. Test-condition
3. Increment/Decrement

1. Initialization

• Before entering into the for loop,first the initialization of loop control variables is done using assignment operator.
• Initialization defines from where the loop should be started to execute.
• Initialization is only performed before entering into the loop and never again.
• We can write multiple Initialization statements seperated by commas.

2. Test-condition

• Test-condition decides when the loop will be terminated.
• If the result of the test-condition is true,then the body of the loop is executed.

3. Increment/Decrement

• This statement allows the loop to repeat by Incrementing or Decrementing the value.
• Increment/Decrement is performed after checking for the condition in the for loop.
• We can also write multiple Increment/Decrement statements seperated by commas.

Example - Printing the the table of Given Number using for loop

class ForLoopEx
{
   public static void main(String args[])
   {
      int i=0,num=5;
      for(i=1;i<=10;i++)
      {
         System.out.println(i * num);
      }
   }
}

Output

Different ways to write For Loop

1. Without writting initialization statement

We can write for loop without writting initialization statement. But semicolon is necessary in the condition.

Loop will execute just like above example.

int i=0,num=5;
for( ; i<=10; i++)
{
    System.out.println(i * num);
}

Output: table of 5

2. Without writting Initialization and Increment/Decrement statement

We can also write the for loop without using Initialization and Increment/Decrement statement.But semicolon is necessary in both the conditions.

We can provide Increment/Decrement inside the body of the loop.

int i=0,num=5;
for( ; i<=10; )
{
    System.out.println(i * num);
    i++;
}

Output: table of 5

3. Without writting anything inside the for loop.

We can also write the for loop without using any statement out of 3. This for loop will cause an infinite loop.

int i=0,num=5;
for( ; ; )
{
    System.out.println(i * num);
    i++;
}   

Output: table of 5 to Inifinite numbers

4. Multiple initializations inside the for loop

We can write more than one initializers inside the for loop.

int i=0,num=0;
for( i=1,num=5; i<=10 ;i++ )
{
    System.out.println(i * num);
}   

Output: table of 5

5. Multiple initializations and Increments inside the for loop

We can also write more than one initializations and Increments inside the for loop.

int i=0,num=0,result=0;

for( i=1,num=5,result=num ; i<=10 ; i++,result=i*num)
{
    System.out.println(result);
}