Java Tutorial/Statement Control/For Each Loop

Iterating over Multidimensional Arrays: Use for-each style for on a two-dimensional array

public class MainClass {
  public static void main(String args[]) {
    int sum = 0;
    int nums[][] = new int[3][5];
    // give nums some values
    for (int i = 0; i < 3; i++)
      for (int j = 0; j < 5; j++)
        nums[i][j] = (i + 1) * (j + 1);
    // use for-each for to display and sum the values
    for (int x[] : nums) {
      for (int y : x) {
        System.out.println("Value is: " + y);
        sum += y;
      }
    }
    System.out.println("Summation: " + sum);
  }
}

Value is: 1
Value is: 2
Value is: 3
Value is: 4
Value is: 5
Value is: 2
Value is: 4
Value is: 6
Value is: 8
Value is: 10
Value is: 3
Value is: 6
Value is: 9
Value is: 12
Value is: 15
Summation: 90

The for each loop for an enum data type

for (type identifier : iterable_expression) {
  // statements
}

The season is now spring
 The season is now summer
 The season is now fall
 The season is now winter

The for-each loop is essentially read-only

public class MainClass {
  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
    }
   
    System.out.println();
    for(int x : nums) 
      System.out.print(x + " "); 
    System.out.println();
  }  
}

1 2 3 4 5 6 7 8 9 10 
1 2 3 4 5 6 7 8 9 10

The For-Each Version of the for Loop

The general form of the for-each version of the for is shown here:

for(type itr-var : iterableObj) statement-block

The object referred to by iterableObj must be an array or an object that implements the new Iterable interface.

Use a for-each style for loop

public class MainClass { 
  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; 
    } 
    System.out.println("Summation: " + sum);
  } 
}

Value is: 1
Value is: 2
Value is: 3
Value is: 4
Value is: 5
Value is: 6
Value is: 7
Value is: 8
Value is: 9
Value is: 10
Summation: 55

Using break with a for-each-style for

public class MainClass {
  public static void main(String args[]) {
    int sum = 0;
    int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    // Use for to display and sum the values.
    for (int x : nums) {
      System.out.println("Value is: " + x);
      sum += x;
      if (x == 5){
        break; // stop the loop when 5 is obtained
      }
    }
    System.out.println("Summation of first 5 elements: " + sum);
  }
}

Value is: 1
Value is: 2
Value is: 3
Value is: 4
Value is: 5
Summation of first 5 elements: 15

Using "for each" to loop through array

public class MainClass {
  public static void main(String[] arg) {
    char[] vowels = { "a", "e", "i", "o", "u"};
    
    for(char ch: vowels){
      System.out.println(ch);
    }
  }
}

a
e
i
o
u

Using the For-Each Loop with Collections: ArrayList

For-Each Loop can be used to any object that implements the Iterable interface. This includes all collections defined by the Collections Framework,

import java.util.ArrayList;
 
public class MainClass { 
    
  public static void main(String args[]) { 
    ArrayList<Double> list = new ArrayList<Double>();
    list.add(10.14);
    list.add(20.22);
    list.add(30.78);
    list.add(40.46);
    double sum = 0.0;
    for(double itr : list)
      sum = sum + itr;
    System.out.println(sum);
  
  } 
}

101.6