面向对象-ArrayList练习

水深无声 2022-05-29 04:12 247阅读 0赞

元素很多，涉及到频繁的增删操作，使用LinkedList；涉及到增删，还有查询，使用ArrayList。

1、去除重复元素：

代码：

import java.util.*;
    
    public class code
    {	
    	public static void main(String[] args) {
    		ArrayList al = new ArrayList();
    		
    		al.add("1");
    		al.add("2");
    		al.add("1");
    		al.add("2");
    		al.add("1");
    		
    		sop(al);
    		al = Single(al);
    		sop(al);
    		//在迭代时循环中next调用一次，就要hasNext判断一次。
    //		Iterator it = al.iterator();
    //		while(it.hasNext()) {
    //			sop(it.next()+"---"+it.next());
    //		}
    	}
    	
    	public static ArrayList Single(ArrayList al) {
    		ArrayList newal = new ArrayList();
    		Iterator it = al.iterator();
    		
    		while(it.hasNext()) {
    			Object obj = it.next();
    			if(!newal.contains(obj))
    				newal.add(obj);
    		}
    		return newal;
    	}
    	
    	public static void sop(Object obj) {
    		System.out.println(obj);
    	}
    }

2、去除相同元素的实例

List集合判断元素是否相同，依据是元素的equals方法。

代码：

import java.util.*;
    
    class Person
    {
    	private String name;
    	private int age;
    	
    	Person(String name,int age) {
    		this.name = name;
    		this.age = age;
    	}
    	
    	public boolean equals(Object obj) {
    		if(!(obj instanceof Person))
    			return false;
    		Person p = (Person)obj;
    		System.out.println(this.name+"--"+p.name);
    		return this.name.equals(p.name) && this.age==age;
    	}
    	
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public int getAge() {
    		return age;
    	}
    
    	public void setAge(int age) {
    		this.age = age;
    	}
    	
    }
    
    public class code
    {	
    	public static void main(String[] args) {
    		ArrayList al = new ArrayList();
    		
    		al.add(new Person("zhangsan",1));
    		al.add(new Person("lisi",2));
    		al.add(new Person("zhangsan",1));
    		al.add(new Person("lisi",2));
    		al.add(new Person("wangwu",3));
    		
    		al = Single(al);
    		
    		Iterator it = al.iterator();
    		while(it.hasNext()) {
    			Person p = (Person)it.next();
    			sop(p.getName()+"--"+p.getAge());
    		}
    		
    	}
    	
    	public static ArrayList Single(ArrayList al) {
    		ArrayList newal = new ArrayList();
    		Iterator it = al.iterator();
    		
    		while(it.hasNext()) {
    			Object obj = it.next();
    			if(!newal.contains(obj))
    				newal.add(obj);
    		}
    		return newal;
    	}
    	
    	public static void sop(Object obj) {
    		System.out.println(obj);
    	}
    }