list Interface:
An ordered set access element, which is a set with the index, there may be repeated in the collection element.
import java.util.ArrayList;
import java.util.List;
{class Demo01 public
public static void main (String [] args) {
List <String> = new new List the ArrayList <String> ();
List.add ( "123");
List.add ( "ABC");
// in insert the specified position specified element
List.add (. 1, "456");
// delete the specified position on the element
String list.remove S = (. 1);
System.out.println ( "delete element is" + s);
// the specified position on the element replacement
String a = list.set (0, "pig Page");
System.out.println ( "alternative elements" a +);
// iterate
for (int i = 0 ; I <list.size (); I ++) {
System.out.println (List.get (I));
}
}
}
Iterator concurrent modification anomalies
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
{class Demo02 public
public static void main (String [] args) {
List <String> new new ARR = the ArrayList <String> ();
arr.add ( "A");
arr.add ( "B");
arr.add ( "C");
// while traversing determines whether "b" element in the set, if a location is added to the "D"
// Get iterator object
iterator <String> it = arr.iterator ( ) ;
the while (it.hasNext ()) {
String it.next S = ();
IF (s.equals ( "B")) {
arr.add ( "D");
}
}
}
}
Storing the set of data structures List
Stack, array, queue, list
LinkedList collection
LinkedList data storage structure is a set of linked list structure
import java.util.LinkedList;
import java.util.List;
public class Demo03 {
public static void main(String[] args) {
LinkedList<String> arr=new LinkedList<String>();
arr.addFirst("a");
arr.addFirst("b");
arr.addLast("c");
arr.addLast("d");
//获取集合中第一个元素
System.out.println("集合中第一个元素为"+arr.getFirst());
//获取集合中最后一个元素
System.out.println("集合中最后一个元素为"+arr.getLast());
//删除集合中第一个元素
arr.removeFirst();
arr.removeFirst();
//删除集合中最后一个元素
arr.removeLast();
for(String s:arr){
System.out.println(s);
}
if(!arr.isEmpty()){
System.out.println("该集合不为空");
}
}
}
Vector集合
Vector集合数据存储的结构是数组结构,为JDK中最早提供的集合。
取出方式:枚举Enumeration。
Vector集合已被ArrayList替代,枚举Enumeration已被迭代器Iterator替代。
set接口
HashSet集合:此类实现Set接口,由哈希表支持(实际上是一个 HashMap集合)。HashSet集合不能保证的迭代顺序与元素存储顺序相同。
保证HashSet集合元素的唯一,其实就是根据对象的hashCode和equals方法来决定的。
import java.util.HashSet;
public class Demo01 {
public static void main(String[] args) {
HashSet<String> set=new HashSet<String>();
set.add("a");
set.add("a");
set.add("b");
//遍历
for(String s:set){
System.out.println(s);
}
}
}
public class Demo02 {
public static void main(String[] args) {
String a="abc";
String b="abc";
System.out.println(a.hashCode());
System.out.println(b.hashCode());
}
}
public class Demo04 {
public static void main(String[] args) {
LinkedHashSet<String> set=new LinkedHashSet<String>();
set.add("abc");
set.add("aaa");
set.add("bcd");
set.add("abc");
for(String s:set){
System.out.println(s);
}
}
}