java - Java，哈希图，无法打印值（对象）

Question

我的代码：

HashMap<Integer,Student> Chemistry= new HashMap<Integer,Student>();
Chemistry.put(3333,"NICK");
for (int keys : Chemistry.keySet()){
             System.out.println(keys + ":"+ Chemistry.get(keys));
 }

输出是：

3333:Student@4aa298b7

标签： javaprintinghashmap

Answer 1

toString()这是您看到的默认实现。您可以覆盖它以获得更有用的东西。例如：

public class Student {
    private String name;

    // Constructors, methods, the whole nine yards...

    @Override
    public String toString() {
        return "A student called " + name;
    }
}