Java集合框架List接口与实现类

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List接口

List子接口

代码演示：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

public class Test02 {
    public static void main(String[] args) {
        List list = new ArrayList();
        //1.add()添加元素
        list.add("java");
        list.add("python");
        list.add(0,"c++");
        System.out.println("元素个数：" + list.size());
        System.out.println(list.toString());
        //2.remove()删除元素
        list.remove(0);
        System.out.println("删除之后元素个数：" + list.size());
        System.out.println(list.toString());
        //3.遍历
        System.out.println("--------3.1for遍历---------");
        for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i));
        }
        System.out.println("--------3.2增强for---------");
        for (Object object:list
             ) {
            System.out.println(object);
        }
        System.out.println("--------3.3迭代器---------");
        Iterator iterator = list.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }
        System.out.println("--------3.4列表迭代器---------");
        //可以向前或向后遍历，可以添加、修改、删除元素
        ListIterator listIterator = list.listIterator();
        System.out.println("--------从前往后遍历----------");
        while (listIterator.hasNext()){
            System.out.println(listIterator.nextIndex() + ":" + listIterator.next());
        }
        System.out.println("--------从后往前遍历----------");
        while (listIterator.hasPrevious()){
            System.out.println(listIterator.previousIndex() + ":" + listIterator.previous());
        }
        //4.判断
        System.out.println(list.contains("c"));
        System.out.println(list.isEmpty());
        //5.获取位置
        System.out.println(list.indexOf("java"));
    }
}

结果：

import java.util.ArrayList;
import java.util.List;

public class Test03 {
    public static void main(String[] args) {
        List list = new ArrayList();
        //1.添加数字数据（自动装箱）
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        System.out.println("元素个数" + ":" + list.size());
        System.out.println(list.toString());
        //2.删除操作
        list.remove(0);
        System.out.println("删除后元素的个数：" + list.size());
        System.out.println(list.toString());
        //3.sublist(),返回子集合，含头不含尾
        List sublist = list.subList(1,3);
        System.out.println(sublist.toString());
    }
}

结果：

List实现类

ArrayList使用

代码演示：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.ListIterator;

public class Test04 {
    public static void main(String[] args) {
        ArrayList arrayList = new ArrayList();
        Student s1 = new Student("www",23);
        Student s2 = new Student("sss",25);
        Student s3 = new Student("aaa",24);
        arrayList.add(s1);
        arrayList.add(s2);
        arrayList.add(s3);
        System.out.println("元素个数：" + arrayList.size());
        System.out.println(arrayList.toString());
        //使用迭代器
        Iterator iterator = arrayList.iterator();
        while (iterator.hasNext()){
            Student student = (Student)iterator.next();
            System.out.println(student.toString());
        }
        //使用列表迭代器(顺序)
        ListIterator listIterator = arrayList.listIterator();
        while (listIterator.hasNext()){
            Student student = (Student)listIterator.next();
            System.out.println(student.toString());
        }
        //列表迭代器（逆序）
        while (listIterator.hasPrevious()){
            Student student = (Student)listIterator.previous();
            System.out.println(student.toString());
        }
        //4.判断
        System.out.println(arrayList.contains(new Student("aaa",56)));
        System.out.println(arrayList.isEmpty());
        //5.查找
        System.out.println(arrayList.indexOf(s2));
    }
}

代码结果：

源码分析

• DEFAULT_CAPACITY = 10;默认容量
• 如果没有向集合中添加任何元素时，容量是0，添加一个元素后容量为10，超过进行扩容每次扩大原来的1.5倍
• elementData：存放元素的数组
• size：实际元素个数

Vector使用

代码演示;

import java.util.Enumeration;
import java.util.Vector;

public class Test05 {
    public static void main(String[] args) {
        Vector vector = new Vector();
        //1.添加元素
        vector.add("java");
        vector.add("python");
        vector.add("C++");
        System.out.println("元素个数：" + vector.size());
        //2.删除
//        vector.remove(0);
//        vector.remove("java");
//        vector.clear();
        //3.遍历，使用枚举器
        Enumeration enumeration = vector.elements();
        while (enumeration.hasMoreElements()){
            String str = (String)enumeration.nextElement();
            System.out.println(str);
        }
        //4.判断
        System.out.println(vector.contains("java"));
        System.out.println(vector.isEmpty());
    }
}

代码结果：

LinkedList的使用

代码演示：

import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;

public class Test06 {
    public static void main(String[] args) {
        LinkedList linkedList = new LinkedList();
        Student s1 = new Student("www",23);
        Student s2 = new Student("sss",25);
        Student s3 = new Student("aaa",24);
        //1.添加
        linkedList.add(s1);
        linkedList.add(s2);
        linkedList.add(s3);
        System.out.println("元素个数：" + linkedList.size());
        System.out.println(linkedList.toString());
        //2.删除
//        linkedList.remove(0);
//        linkedList.remove(s1);
//        linkedList.clear();
        //3.遍历
        System.out.println("--------for遍历---------");
        for (int i = 0; i < linkedList.size(); i++) {
            System.out.println(linkedList.get(i));
        }
        System.out.println("--------增强for---------");
        for (Object object:linkedList
             ) {
            Student student = (Student)object;
            System.out.println(student.toString());
        }
        System.out.println("--------使用迭代器---------");
        Iterator iterator = linkedList.listIterator();
        while (iterator.hasNext()){
            Student student = (Student)iterator.next();
            System.out.println(student.toString());
        }
        System.out.println("--------列表迭代器---------");
        ListIterator listIterator = linkedList.listIterator();
        while (listIterator.hasNext()){
            Student student = (Student)listIterator.next();
            System.out.println(student.toString());
        }
        //4.判断
        System.out.println(linkedList.contains(s1));
        System.out.println(linkedList.isEmpty());
        //5.获取索引
        System.out.println(linkedList.indexOf(s2));
    }
}

代码结果：

ArrayList和LinkedList的区别

不同结构实现方式