Answer by mightyWOZ for In detail, how does the 'for each' loop work in Java?

As many of other answers correctly state, the for each loop is just syntactic sugar over the same old for loop and the compiler translates it to the same old for loop.

javac (OpenJDK) has a switch, -XD-printflat, which generates a Java file with all the syntactic sugar removed. The complete command looks like this:

javac -XD-printflat -d src/ MyFile.java//-d is used to specify the directory for output java file

So let’s remove the syntactical sugar

To answer this question, I created a file and wrote two versions of for each, 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 along with the other syntactic sugar (Autoboxing), for each loops got changed to simple loops.