Java

Java : for loop

6 Comments

The for loop in Java is a control flow statement used to iterate a part of the program several times. It’s most preferred when the number of the iteration is fixed.

In for loop are used in three ways :

  1. Simple For Loop
  2. Enhanced For Loop or For-each
  3. Labeled For Loop

Java Simple For Loop

In java, simple for loop is the same as C/C++. It consists of four parts:

Syntax


for(initialization;condition;increment/decrement){  
// code to be executed 
}
  • Initialization (Optional): It is the initialization condition which is executed once when the loop starts. We can initialize the variable or use an already initialized variable.
  • Condition (Optional): It is executed each time to test the condition of the loop. It return boolean values true or false but continues execution depend on until the condition is true.
  • Statement: The statement inside the loop is executed each time until the second condition is false.
  • Increment/Decrement (Optional): It increments or decrements the intialization variable value.

For Loop Flow Chart

for loop flow chart

Example:

Program to print even numbers between 1 to 20

public class SimpleForLoopExample {

	public static void main(String[] args) {
		System.out.println("Even Numbers between 1 to 20 :");
		for (int i = 1; i <= 20; i++) {
			// If modulus of number after devision 2 is 0 then even number
			if (i % 2 == 0) {
				System.out.println(i);
			}
		}
	}
}

Output


Even Numbers between 1 to 20 :
2
4
6
8
10
12
14
16
18
20

Java Nested For Loop

If we have a loop inside a loop that is called as nested loop. For each iteration of outer loop inner loop executes completely.

Example:
Print table for 1 to 10

public class NestedForLoop {

	public static void main(String[] args) {
     for(int i=1;i<=10;i++)
     {
    	 for(int j=1;j<=10;j++)
    	 {
    		System.out.printf("%-3d",(i*j)) ;
    	 }
    	 System.out.println();
     }

	}
}


Output:


1  2  3  4  5  6  7  8  9  10 
2  4  6  8  10 12 14 16 18 20 
3  6  9  12 15 18 21 24 27 30 
4  8  12 16 20 24 28 32 36 40 
5  10 15 20 25 30 35 40 45 50 
6  12 18 24 30 36 42 48 54 60 
7  14 21 28 35 42 49 56 63 70 
8  16 24 32 40 48 56 64 72 80 
9  18 27 36 45 54 63 72 81 90 
10 20 30 40 50 60 70 80 90 100

Java for-each Loop (Java 5+)

The for-each loop is used to traverse object type like array or collection. Java for-each loop is easier than simple for loop because not required to increase or decrese indexes for accessing collections values.

Java for-each loop works on elements basis not index and returns element one by one in the defined variable.

Syntax:


for(Type var:array){  
//code to be executed  
}

Example:

public class ForEachLoopExample {
public static void main(String[] args) {
    //Declaring an array
    int numArr[]={10,20,30,40,50};
    //Print array by using for-each loop
    for(int i:numArr){
        System.out.println(i);
    }
}
}

Output

10
20
30
40
50

Java Labeled For Loop

By using labeled for loop can define a name of loop by using label before the for loop. It’s useful when nested for loop need to break/continue specific for loop.

Usually, break and continue keywords breaks/continues the innermost for loop only.

Syntax:


labelname:  
for(initialization;condition;incr/decr){  
//code to be executed  
}

Example:

public class LabeledForExample {
public static void main(String[] args) {
//Using Label for outer and for loop
aa:
for(int i=1;i<=3;i++){
bb:
for(int j=1;j<=3;j++){
if(i==2;j==2){
break aa;
}
System.out.println(i+""+j);
}
}
}
}

Output:


1 1
1 2
1 3
2 1

If you use break bb;, it will break inner loop only which is the default behavior of any loop.

public class LabeledForExample2 {
public static void main(String[] args) {
aa:
for(int i=1;i<=3;i++){
bb:
for(int j=1;j<=3;j++){
if(i==2&&j==2){
break bb;
}
System.out.println(i+""+j);
}
}
}
}

Output:


1 1
1 2
1 3
2 1
3 1
3 2
3 3

Java Infinitive For Loop

If you use two semicolons ;; in the for loop, it will be infinitive for loop.

Syntax:


for(;;){
//code to be executed
}

Example:

//Java program to demonstrate the use of infinite for loop
//which prints an statement
public class ForExample {
public static void main(String[] args) {
//Using no condition in for loop
for(;;){
System.out.println("infinitive loop");
}
}
}

Output:


infinitive loop
infinitive loop
infinitive loop
infinitive loop
infinitive loop
ctrl+c
Now, you need to press ctrl+c to exit from the program.
Advertisements
Advertisements

Your Feedback Motivate Us

If our FacingIssuesOnIT Experts solutions guide you to resolve your issues and improve your knowledge. Please share your comments, like and subscribe to get notifications for our posts.

Happy Learning !!!

6 thoughts on “Java : for loop”

  3. First of all I would like to say terrific blog! I had
    a quick question which I’d like to ask if you do not mind.
    I was curious to find out how you center yourself
    and clear your head before writing. I’ve had a hard time clearing my thoughts
    in getting my thoughts out there. I do take pleasure
    in writing however it just seems like the first 10 to 15 minutes tend to be wasted just trying to figure out how to begin. Any recommendations or tips?
    Thanks!

    Liked by 1 person

    Reply

Leave a comment