For Loop in Java

For Loop
A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. A for loop is useful when you know how many times a task is to be repeated.

Syntax:
for(initialization; Boolean_expression; update)
{
//Statements
}

Here is the flow of control in a for loop:
The initialization step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears.
Next, the Boolean expression is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and flow of control jumps to the next statement past the for loop.
After the body of the for loop executes, the flow of control jumps back up to the update statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the Boolean expression.
The Boolean expression is now evaluated again. If it is true, the loop executes and the process repeats itself (body of loop, then update step,then Boolean expression). After the Boolean expression is false, the for loop terminates.

Example:
public class Test {
public static void main(String args[]) {
for(int x = 10; x < 20; x = x+1) {
System.out.print("value of x : " + x );
System.out.print("\n");
}
}
}


Enhanced for loop in Java
As of java 5 the enhanced for loop was introduced. This is mainly used for Arrays.

Syntax:
for(declaration : expression)
{
Statements;
}
Declaration : The newly declared block variable, which is of a type compatible with the elements of the array you are accessing. The variable will be available within the for block and its value would be the same as the current array element.
Expression: This evaluate to the array you need to loop through. The expression can be an array variable or method call that returns an array.

Example:
public class Test {
public static void main(String args[]){
int [] numbers = {10, 20, 30, 40, 50};
for(int x : numbers ){
System.out.print( x );
System.out.print(",");
}
System.out.print("\n");
String [] names ={"Ram", "Kailash", "Ankith", "John"};
for( String name : names ) {
System.out.print( name );
System.out.print(",");
}
}
}


The 'break' Keyword
The break keyword is used to stop the entire loop. The break keyword must be used inside any loop or a switch statement.
Syntax:
break;
Example:
public class Test {
public static void main(String args[]) {
int [] numbers = {10, 20, 30, 40, 50};
for(int x : numbers ) {
if( x == 30 ) {
break;
}
System.out.print( x );
System.out.print("\n");
}
}
}


The continue Keyword
The continue keyword can be used in any of the loop control structures. It causes the loop to immediately jump to the next iteration of the loop.
In a for loop, the continue keyword causes flow of control to immediately jump to the update statement. In a while loop or do/while loop, flow of control immediately jumps to the Boolean expression.
Syntax:
continue;

Example:
public class Test {
public static void main(String args[]) {
int [] numbers = {10, 20, 30, 40, 50};
for(int x : numbers ) {
if( x == 30 ) {
continue;
}
System.out.print( x );
System.out.print("\n");
}
}
}