2017.4.13 Java-enhanced for loop for each

The For-each loop is also called an enhanced for loop, or a foreach loop.

The For-each loop is a new feature of JDK5.0 (other new features such as generics, auto-boxing, etc.).

The addition of the For-each loop simplifies the traversal of the collection.

Its syntax is as follows:

for (type Element:array)

{

SYSTEM.OUT.PRINTLN (Element);

}

Example

Its basic use can be directly read the code:

The code first compares two for loops, then implements a two-dimensional array with an enhanced for loop, and finally iterates through a list collection in three ways.

Import Java.util.arraylist;import Java.util.iterator;import Java.util.list;public class foreachtest{public static Voi                D main (string[] args) {int[] arr = {1, 2, 3, 4, 5};        System.out.println ("----------old way Traversal------------");        Legacy mode for (int i=0; i<arr.length; i++) {System.out.println (arr[i]);                } System.out.println ("---------New way to traverse-------------");        New notation, enhanced for loop for (int element:arr) {System.out.println (element);                } System.out.println ("---------traverse two-dimensional array-------------");                Traverse the two-dimensional array int[][] arr2 = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};            For (int[] row:arr2) {for (int element:row) {System.out.println (element); }}//Iterate through the collection in three ways list list<string> list = new Arraylist<string> (                ); List.add ("a");        List.add ("B");                List.add ("C");        SYSTEM.OUT.PRINTLN ("----------mode 1-----------");                    The first way, the normal for loop for (int i = 0; i < list.size (); i++) {System.out.println (List.get (i));        } System.out.println ("----------mode 2-----------");        The second way, use the iterator for (iterator<string> iter = List.iterator (); Iter.hasnext ();)        {System.out.println (Iter.next ());        } System.out.println ("----------mode 3-----------");                    The third way, use the enhanced for loop for (String str:list) {System.out.println (str); }    }}

Disadvantages of the For-each loop: The index information is discarded.

When traversing a collection or array, if you need to access the index of a collection or array, it is best to use the old-fashioned way to loop or traverse, rather than using an enhanced for loop, because it loses subscript information.

2017.4.13 Java-enhanced for loop for each