自定义toString 的调用过程 - 黑马程序员技术交流社区

public class Student implements Comparable<Student> {
private String name;
private int age;
private String address;
public String toString(){
return this.age+this.name;
}
Student (String name ,int age){
this.age=age;
this.name=name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
//自定义哈希值指定集合元素存储到哈希表中
public int hashCode(){
return name.hashCode()+age*32;
}
//自定义比较方法
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;
}
@Override //当集合按二叉树存储时，可以按自然顺序排序
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 class MapTest {
/**
* 需求：取出所有map元素
*/
public static void main(String[] args) {
Map<Student,String> map=new TreeMap<Student,String>();
map.put(new Student("lisi1",123), "tianjingo");
map.put(new Student("lisi2",12), "tianjingo");
map.put(new Student("lisi3",121), "tianjingo");
map.put(new Student("lisi2",127), "tianjingo");
Set<Map.Entry<Student,String>> keySet=map.entrySet();
Iterator<Map.Entry<Student,String>> it=keySet.iterator();
while(it.hasNext()){
Map.Entry<Student,String> me=it.next();
Student key=me.getKey();
String value=me.getValue();
System.out.println(key+"==="+value);
}
}
}

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