Three ways to traverse the list collection in Java (full network details)

　　List collection In the Java daily development is essential, as long as the use of a variety of methods can greatly improve the efficiency of our development, the appropriate use of various methods will make our development more efficient.

I have summed up the traversal of the three list collections, as described below hit.

First, create an entity class for use below.

 Public classnews{Private intID; PrivateString title; PrivateString author;  PublicNews (intID, string title, string author) {        Super();  This. ID =ID;  This. title =title;  This. Author =author; }         Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetTitle () {returntitle; }     Public voidSettitle (String title) { This. title =title; }     PublicString Getauthor () {returnauthor; }     Public voidSetauthor (String author) { This. Author =author; }}

The first Kind, the most basic traversal method: For loop, specify subscript length, use the size () method of the list collection for A For loop traversal

　　

Import java.util.ArrayList;

public class Demo01 {

public static void Main (string[] args) {

arraylist<news> list = new arraylist<news> ();
　　　　
List.add (New News (1, "List1", "a"));
List.add (New News (2, "List2", "B"));
List.add (New News (3, "List3", "C"));
List.add (New News (4, "List4", "D"));

 for (int i = 0; i < list.size (); i++) {            = (News) list.get (i);            System.out.println (S.getid ()+ "  " +s.gettitle () + ""  +S.getauthor ()); }
}
}

The second kind, more concise traversal: Use foreach to traverse the list, but not to manipulate an element (a method that works as well when iterating through arrays and map collections)

Import java.util.ArrayList;  Public class Demo02 {  publicstaticvoid  main (string[] args) {ArrayListnew Ar Raylist<news>();

List.add (New News (1, "List1", "a"));
List.add (New News (2, "List2", "B"));
List.add (New News (3, "List3", "C"));
List.add (New News (4, "List4", "D"));

　　　　 for　　　(News s:list) {            System.out.println (S.getid ()+ "  " +s.gettitle () + "  " +S.getauthor ()); }}}

third , applicable iterator iterator traversal: automatic traversal directly based on the list collection

　　Specific steps:

① uses a list call, iterator () returns an Iterator object;
② uses an Iterator object call, Hasnext () to determine whether there is a next piece of data;
③ is called with an iterator object.

Importjava.util.ArrayList; Public classDemo03 { Public Static voidMain (string[] args) {ArrayList<News> list =NewArraylist<news>(); List.add (NewNews (1, "List1", "a")); List.add (NewNews (2, "List2", "B")); List.add (NewNews (3, "List3", "C")); List.add (NewNews (4, "List4", "D")); Iterator<News> iter =List.iterator ();  while(Iter.hasnext ()) {News s=(News) iter.next (); System.out.println (S.getid ()+ "" "+s.gettitle () +" "+S.getauthor ()); }}}

The above three kinds of traversal methods are not particularly large, can be used when there is no specific requirements. However, according to different special circumstances, we should choose a reasonable way to improve the efficiency of development.

Three ways to traverse the list collection in Java (full network details)