Java For Loop

Loops are used to execute the set of code or instructions over a number of times when the condition is true. Java supports three types of loops -

• For
• While
• do-while

Loop Comparison

for(init;condition;incr/decr){  
// code
}

while(condition){  
//code 
}

do{  
//code  
}while(condition);

for(int i=1;i<=10;i++){  
System.out.println(i);  
}

int i=1;  
while(i<=10){  
System.out.println(i);  
i++;  
}

int i=1;  
do{  
System.out.println(i);  
i++;  
}while(i<=10);

For Loop

If you know the number of iterations already, you can use the for loop statement to execute the program several times if the condition holds true. There are three types of for loops -

• Simple For Loop
• For-each or Enhanced For Loop
• Labeled For Loop

1. Simple for Loop

The syntax is the same as C or C++ . You can initialize the variable in the for expression, check condition, and increment or decrement the variable's value.

• Initialization : It is the first condition that will be executed once the loop starts. You can initialize the variable or use an already initialized variable.
• Condition : It is the second condition that will get executed every time to test the condition of the loop, and execution will be continued until the condition is false. This must return a boolean value, either true or false.
• Statement : The statement of the loop is executed every time until the second condition is false.
• Increment/Decrement : It will increment or decrement the variable value.

Syntax

for(initialization;condition;incr/decr){  
//statement or code to be executed  
}

Example

public class ForExample {  
public static void main(String[] args) {  
    for(int i=1;i<=3;i++){  
        System.out.println(i);  
    }  
}  
}

Output

1
2
3

Nested for Loop

Java allows you to use one for loop inside another for loop . If the outer for loop holds true value only, the inner for loop will execute.

Example

public class NestedForExample {  
public static void main(String[] args) {  
//loop of i  
for(int i=1;i<=3;i++){  
//loop of j  
for(int j=1;j<=3;j++){  
        System.out.println(i+" "+j);  
}//end of i  
}//end of j  
}  
}

Output

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

Pyramid Example

public class PyramidExample {  
public static void main(String[] args) {  
for(int i=1;i<=5;i++){  
for(int j=1;j<=i;j++){  
        System.out.print("* ");  
}  
System.out.println();//new line  
}  
}  
}

Output

* 
* * 
* * * 
* * * * 
* * * * *

2. For-each Loop

You can use a for-each loop for array or collection traversal. It is easier than using a simple loop within mentioning the increment or decrement value. This loop works on the elements, and each element is returned one by one in the variable.

Syntax

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

Example

public class ForEachExample {  
public static void main(String[] args) {  
    //Declaring an array  
    int var[]={1,2,44,5,7};  
    //Printing array using for-each loop  
    for(int i:var){  
        System.out.println(i);  
    }  
}  
}

Output

1
2
44
5
7

3. Labeled for Loop

You can give a name to the for-loop by using a label before the for-loop. It is efficient to use labels if you are working with nested loops.

Syntax

labelname:  
for(initialization;condition;incr/decr){  
//code 
}
Example

public class LabeledForExample {  
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 aa;  
                    }  
                    System.out.println(i+" "+j);  
                }  
        }  
}  
}

Output

1 1
1 2
1 3
2 1

Infinitive for Loop

You can create an infinitive loop by using two semicolons in the for-loop. To exit this infinitive loop, press ctrl + c .

Syntax

for(;;){  
//code 
}

Example

public class ForExample {  
public static void main(String[] args) {  
    for(;;){  
        System.out.println("infinitive loop");  
    }  
}  
}

Output

infinitive loop 

infinitive loop 

infinitive loop

infinitive loop 

infinitive loop 

ctrl+c