Java - For Loop

Java for Loop

The for loop executes a set of statements in each iteration. Whenever, number of iteration is known, for loop is preferred over while loop.

Syntax

for(initialization(s); condition(s); counter_update(s);){
  statements;
} 

• Initialization(s): Variable(s) is initialized in this section and executed for one time only.
• Condition(s): Condition(s) is defined in this section and executed at the start of loop everytime.
• Counter Update(s): Loop counter(s) is updated in this section and executed at the end of loop everytime.

Flow Diagram:

Example:

In the example below, the program continue to print variable called i from value 1 to 5. After that, it exits from the for loop.

public class MyClass {
  public static void main(String[] args) {
    for (int i = 1; i <= 5; i++)
      System.out.println(i);  
  }
}

The output of the above code will be:

1
2
3
4
5

Example

Multiple initializations, condition checks and loop counter updates can be performed in a single for loop. In the example below, two variable called i and j are initialized, multiple conditions are checked and multiple variables are updated in a single for loop.

public class MyClass {
  public static void main(String[] args) {
    for (int i = 1, j = 100;   i <= 5 || j <= 800;   i++, j = j + 100)
      System.out.println("i="+i+", j="+j);  
  }
}

The output of the above code will be:

i=1, j=100
i=2, j=200
i=3, j=300
i=4, j=400
i=5, j=500
i=6, j=600
i=7, j=700
i=8, j=800

Java for-each Loop

Java for-each loop is used to traverse an array or a collection. In each iteration of the loop, current element is assigned to a user-defined variable and array/collection pointer is moved to next element which is processed in the next iteration. Please note that it works on element basis (not index basis).

Syntax

for(variable: array/collection){
  statements;
} 

In the example below, the foreach loop is used on array called Arr which is further used to print each element of the array in each iteration.

public class MyClass {
  public static void main(String[] args) {
    int Arr[]={10, 20, 30, 40 ,50};
    
    System.out.println("The Arr contains:");
    for(int i: Arr) 
       System.out.println(i);
  }
}

The output of the above code will be:

The Arr contains:
10
20
30
40
50