Java集合框架

Posted 2020-11-03 H+

Collection框架Demo（java.util.Collection）

1，Collection集合的基本Demo:

package com.hpioneer.collection;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Objects;

/**
 * @Description: ColLection转数组遍历
 * @Author: HPioneer
 * @CreateTime: 2018/5/7  17:40
 * @File: Collection of JavaProject in com.hpioneer.collection
 * @FullFileName: com.hpioneer.collection.Collection
 * @Create By IntelliJ
 * @Version: 1.0
 */
public class Demo_Collection {
    public static void main(String[] args) {
        Collection c = new ArrayList();

        boolean b1 = c.add("abc");
        boolean b2 = c.add(true);                            //自动装箱new Boolean(true);
        boolean b3 = c.add(100);
        boolean b4 = c.add(new Student("张三",23));
        boolean b5 = c.add("abc");

        System.out.println(b1);
        System.out.println(b2);
        System.out.println(b3);
        System.out.println(b4);
        System.out.println(b5);

        System.out.println(c.toString());

        Object[] arr = c.toArray();

        for (int i =0 ;i<arr.length;i++){
            System.out.println(arr[i]);
        }
        System.out.println(c.size());
        System.out.println(c);
    }
}

2，Collection迭代器遍历

package com.hpioneer.collection;

import sun.plugin.WJcovUtil;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

/**
 * @Description:
 * @Author: HPioneer
 * @CreateTime: 2018/5/7  17:51
 * @File: Iterator of JavaProject in com.hpioneer.collection
 * @FullFileName: com.hpioneer.collection.Iterator
 * @Create By IntelliJ
 * @Version: 1.0
 */
public class Demo_Iterator {
    public static void main(String[] args) {
        Collection c = new ArrayList();
        c.add(new Student("张三",23));
        c.add(new Student("李四",25));
        c.add(new Student("王五",25));

        Iterator it = c.iterator();
        while (it.hasNext()){
            Student s = (Student) it.next();
            System.out.println(s.getName()+" "+s.getAge());
        }
    }
}

3，ListIterator

package com.hpioneer.collection;

import java.util.List;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Objects;
import java.util.ListIterator;

/**
 * @Description: ListIterator的add,遍历元素，集合修改元素
 * @Author: HPioneer
 * @CreateTime: 2018/5/7  17:40
 * @File: Collection of JavaProject in com.hpioneer.collection
 * @FullFileName: com.hpioneer.collection.Collection
 * @Create By IntelliJ
 * @Version: 1.0
 */
public class Demo_Collection {
    public static void main(String[] args) {
  
        List list = new ArrayList();
        list.add("a");                             //Object obj = new String();
        list.add("b");
        list.add("world");
        list.add("c");
        list.add("d");
        list.add("e");
        ListIterator lit = list.listIterator();   //获取迭代器(List集合特有的)
        while(lit.hasNext()) {
            String str = (String)lit.next();     //向下转型
            if("world".equals(str)) {
                //list.add("javaee");            //遍历的同时在增加元素,并发修改ConcurrentModificationException
                lit.add("javaee");
            }
        }

        System.out.println(list);
    }
}

4，Vector的迭代

package com.hpioneer.collection;

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

/**
 * @Description:
 * @Author: HPioneer
 * @CreateTime: 2018/5/7  18:14
 * @File: Demo_Vector of JavaProject in com.hpioneer.collection
 * @FullFileName: com.hpioneer.collection.Demo_Vector
 * @Create By IntelliJ
 * @Version: 1.0
 */
public class Demo_Vector {
    public static void main(String[] args) {
        Vector v = new Vector();
        v.addElement("a");
        v.addElement("b");
        v.addElement("c");
        v.addElement("d");

        Enumeration en = v.elements();                    //获取枚举
        while(en.hasMoreElements()) {                    //判断集合中是否有元素
            System.out.println(en.nextElement());        //获取集合中的元素
        }
    }
}