面向对象-ArrayList练习

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);
	}
}