集合（4）

练习：去除arraylist中的重复元素【string】  

package songyan;

import java.util.ArrayList;

public class test{
    public static void main(String[] args)
    {
        ArrayList al= new ArrayList();
        al.add("name1");
        al.add("name2");
        al.add("name1");
        al.add("name2");
        test t= new test();
        al=t.getlist(al);
        System.out.println( al); 
    }
    
    public static ArrayList getlist(ArrayList al)
    {
        ArrayList al2= new ArrayList();
        for(int i=0;i<al.size();i++)
        {
            if(!al2.contains(al.get(i)))
            {
                al2.add(al.get(i));
            }
        }
        return al2;
    }
}

去除arraylist中的重复元素【自定义类型】

package songyan;

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

class Dog{
    public String name;
    Dog(String name)
    {
        this.name=name;
    }
    Dog()
    {
        
    }
}
public class test{
    public static void main(String[] args)
    {
        ArrayList al= new ArrayList();
        Dog d1= new Dog("name1");
        Dog d2= new Dog("name2");
        Dog d3= new Dog("name3");
        Dog d4= new Dog("name4");
        al.add(d1);
        al.add(d2);
        al.add(d1);

package songyan;

 

import java.util.ArrayList;

import java.util.Iterator;

 

class Dog{

   public String name;

   Dog(String name)

   {

      this.name=name;

   }

   Dog()

   {

     

   }

}

publicclass test{

   publicstaticvoid main(String[] args)

   {

      ArrayList al= new ArrayList();

      Dog d1= new Dog("name1");

      Dog d2= new Dog("name2");

      Dog d3= new Dog("name3");

      Dog d4= new Dog("name4");

      al.add(d1);

      al.add(d2);

      al.add(d1);