Java for each loop statement

Introduction

A for-each style loop can loop through a collection of objects, such as an array.

The for-each loop is also called the enhanced for loop.

The general form of the for-each loop: 

for(type itr-var : collection){
   statement-block 
}

Here, type specifies the type and itr-var specifies the name of an iteration variable.

itr-var will receive the elements from a collection, one at a time, from beginning to end.

The following code uses a traditional for loop to compute the sum of the values in an array: 

int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };  
int sum = 0;  
  
for(int i=0; i < 10; i++){
   sum += nums[i]; 
}

The follow code uses a for-each loop: 

int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };  
int sum = 0;  
           
for(int x: nums){
    sum += x; 
}

Here is an entire program that demonstrates the for-each loop: 

// Use a for-each style for loop. 
public class Main {  
  public static void main(String args[]) {  
    int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };  
    int sum = 0;  
 
    // use for-each style for to display and sum the values 
    for(int x : nums) {  
      System.out.println("Value is: " + x); 
      sum += x;  /*  w  w  w  .  j a  v  a2 s  .c om*/
    }  
 
    System.out.println("Summation: " + sum); 
  }  
}

for each loop is read-only

The for-each loop variable is "read-only".

Updating to the iteration variable has no effect on the underlying collection.

For example, consider this program: 

// The for-each loop is essentially read-only. 
public class Main {   
  public static void main(String args[]) {   
    int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };   
  
    for(int x : nums) {   
      System.out.print(x + " ");  
      x = x * 10; // no effect on nums 
    }   //from  w w w  .  ja v  a  2s.  co  m
    
    System.out.println(); 
 
    for(int x : nums)  
      System.out.print(x + " ");  
 
    System.out.println(); 
  }   
}



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