Question

怎么遍历HashMap中的ArrayList,运行结果乱码了，程序在下面。求大神支援

import java.util.*;
import java.util.Map.Entry;

public class Movie3 {
int movieId;
String movieName;
double price;
public Movie3(int movieId, String movieName,double price) {
this.movieId = movieId;
this.movieName = movieName;
this.price = price;
}
public int getID(){
return movieId;
}
public String getMovieName(){
return movieName;
}
public double getPrice(){
return price;
}
public static void main(String[] args){
Movie3 a=new Movie3(1,"冰雪奇缘",40);
Movie3 b=new Movie3(2,"美国队长2",40);
Movie3 c=new Movie3(3,"大闹天宫",50);
Movie3 d=new Movie3(4,"卑鄙的我2",50);
List sciencemovieDVDList=new ArrayList();
List AnimationmovieDVDList=new ArrayList();
sciencemovieDVDList.add(b);
sciencemovieDVDList.add(c);
AnimationmovieDVDList.add(a);
AnimationmovieDVDList.add(d);
Map movies=new HashMap();
movies.put("科幻电影",sciencemovieDVDList);
movies.put("动漫电影",AnimationmovieDVDList);
System.out.println("键的集合" + movies.keySet());
System.out.println("键-值对集合：" + movies);
String key = "科幻电影";
if (movies.containsKey(key)) {
System.out.println("键“"+key+"”对应的值："+movies.get(key));
}
movies.remove(key);
System.out.println("键-值”对集合："+ movies);

}
}

Answer 1

乱码？？？？？你加个tostring方法，不是乱不乱码，一看就是菜鸟

package image;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Movie3
{
	int movieId;
	String movieName;
	double price;

	public Movie3 ( int movieId, String movieName, double price )
	{
		this.movieId = movieId;
		this.movieName = movieName;
		this.price = price;
	}

	public int getID ()
	{
		return movieId;
	}

	public String getMovieName ()
	{
		return movieName;
	}

	public double getPrice ()
	{
		return price;
	}

	@Override
	public String toString ()
	{
		StringBuilder builder = new StringBuilder ();
		builder.append ("Movie3 [movieId=");
		builder.append (movieId);
		builder.append (", movieName=");
		builder.append (movieName);
		builder.append (", price=");
		builder.append (price);
		builder.append ("]");
		return builder.toString ();
	}

	public static void main ( String[] args )
	{
		Movie3 a = new Movie3 (1, "冰雪奇缘", 40);
		Movie3 b = new Movie3 (2, "美国队长2", 40);
		Movie3 c = new Movie3 (3, "大闹天宫", 50);
		Movie3 d = new Movie3 (4, "卑鄙的我2", 50);
		List sciencemovieDVDList = new ArrayList ();
		List AnimationmovieDVDList = new ArrayList ();
		sciencemovieDVDList.add (b);
		sciencemovieDVDList.add (c);
		AnimationmovieDVDList.add (a);
		AnimationmovieDVDList.add (d);
		Map movies = new HashMap ();
		movies.put ("科幻电影", sciencemovieDVDList);
		movies.put ("动漫电影", AnimationmovieDVDList);
		System.out.println ("键的集合" + movies.keySet ());
		System.out.println ("键-值对集合：" + movies);
		String key = "科幻电影";
		if (movies.containsKey (key))
		{
			System.out.println ("键“" + key + "”对应的值：" + movies.get (key));
		}
		movies.remove (key);
		System.out.println ("键-值”对集合：" + movies);
	}
}

追问

能解释下那个to string方法吗？大神，我刚学JAVA

追答

tostring方法就是指将一些模型信息打印成有条理的内容，不是原始的Object的tostring方法，原始的没有意义，所以就是乱码，然后一般情况下，只要有setter和getter的model数据类对象时，都要有tostring方法的覆盖，返回该类有意义的内容，详见：java十大低级错误