Answer by mightyWOZ for How does the Java 'for each' loop work?

As many of other answers correctly state, the foreachloop is just syntactic sugar over the same old forloop.

You can see the actual for loop to which it is translated by using the -XD-printflat switch for javac (open jdk).

javac -XD-printflat -d src/ MyFile.java

-d is used to specify the directory for output java file

When you use this switch the compiler generates a new java file with all the syntactic sugar removed.(ie for each converted to same old for loop)

Lets remove the syntactical sugar

To answer this question, I created a file and wrote two version of foreach, one with array and another with a list. my java file looked like this.

import java.util.*;
public class Temp{

    private static void forEachArray(){
        int[] arr = new int[]{1,2,3,4,5};
        for(int i: arr){
            System.out.print(i);
        }
    }

    private static void forEachList(){
        List<Integer> list = Arrays.asList(1,2,3,4,5);
        for(Integer i: list){
            System.out.print(i);
        }
    }
}

When I compiled this file with above switch, I got the following output.

import java.util.*;

public class Temp {

    public Temp() {
        super();
    }

    private static void forEachArray() {
        int[] arr = new int[]{1, 2, 3, 4, 5};
        for (/*synthetic*/ int[] arr$ = arr, len$ = arr$.length, i$ = 0; i$ < len$; ++i$) {
            int i = arr$[i$];
            {
                System.out.print(i);
            }
        }
    }

    private static void forEachList() {
        List list = Arrays.asList(new Integer[]{Integer.valueOf(1), Integer.valueOf(2), Integer.valueOf(3), Integer.valueOf(4), Integer.valueOf(5)});
        for (/*synthetic*/ Iterator i$ = list.iterator(); i$.hasNext(); ) {
            Integer i = (Integer)i$.next();
            {
                System.out.print(i);
            }
        }
    }
}

You can see that with other syntactic sugar (Autoboxing) for each loops got changed to simple loops.