HashMap中键值访问对象的问题
import java.util.*;
public class Exp2
{
public static void main(String[] args){
HashMap<Element, Figureout> h2=new HashMap<Element, Figureout>();
for(int i=0;i<5;i++)
h2.put(new Element(i), new Figureout());
System.out.println("h2:");
System.out.println("Get the result for Element:");
Element test=new Element(5);
if(h2.containsKey(test))
System.out.println((Figureout)h2.get(test));
else
System.out.println("Not found");
}
}
class Element
{
int number;
public Element(int n)
{
number=n;
}
}
class Figureout
{
Random r=new Random();
boolean possible=r.nextDouble()>0.5;
public String toString()
{
if(possible)
return "OK!";
else
return "Impossible!";
}
}
上面的程序是创建HashMap 输出键值是 Element test=new Element(5)对应的对象new Figureout()，这儿 if(h2.containsKey(test)) 判断是错误的，也就是没有找到相等的
键值,这是为什么。怎样才能使if条件成立，执行toString()
[解决办法]
你用类对象做键值，好像要重写该类的hashCode()和equals()方法吧
