本帖最后由 HM许涛 于 2013-4-25 22:29 编辑
学习黑马毕向东老师基础视频中案例,在Map练习中需要用到定义的Student类。在注释掉最后三个方法的情况下,编译通过,运行结果如下:
输出完成 (耗时 0 秒) - 正常终止
将最后的toString注释去掉后,运行正常了。个人理解是第一个没有toString方法,返回了内存的位置。有了以后,返回了具体值。不知道对不对。
有没哪位大神能说一下toString有和没有的实现原理?
import java.util.*;
class Noname1
{
public static void main(String[]args)
{
TreeMap<Student,String>tm=new TreeMap<Student,String>();
tm.put(new Student("lisi1",23),"beij");
tm.put(new Student("lisi2",22),"nanij");
tm.put(new Student("lisi3",25),"hj");
tm.put(new Student("lisi4",26),"sij");
Set<Map.Entry<Student,String>>entrySet=tm.entrySet();
Iterator<Map.Entry<Student,String>>it=entrySet.iterator();
while(it.hasNext())
{
Map.Entry<Student,String>me=it.next();
Student stu=me.getKey();
String addr=me.getValue();
System.out.println(stu+"::::"+addr);
}
}
}
class Student implements Comparable<Student>
{
public String name;
public int age;
Student(String name,int age)
{
this.name=name;
this.age=age;
}
public int compareTo(Student s)
{
int num=new Integer(this.age).compareTo(new Integer(s.age));
if(num==0)
return this.name.compareTo(s.name);
return num;
}
public int hashCode()
{
return name.hashCode()+age*23;
}
public boolean equals(Object obj)
{
if(!(obj instanceof Student))
throw new ClassCastException("类型不匹配");
Student s=(Student)obj;
return this.name.equals(s.name)&&this.age==s.age;
}
/*public String getName()
{
return name;
}
public int getAge()
{
return age;
}
public String toString()
{
return name+":::::"+age;
}*/
}
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