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案例演示
package project;
import java.util.ArrayList;
importjava.util.Comparator;
import java.util.TreeSet;
public class Demo_Genric {
/**
*泛型固定下边界
*? super E
*
*泛型固定上边界
*? extends E
*/
public static void main(String[] args) {
TreeSet<Student> ts1 = new TreeSet<>(new CompareByAge());
ts1.add(new Student("张三",23));
ts1.add(new Student("李四",24));
System.out.println(ts1);
TreeSet<BaseStudent> ts2 = new TreeSet<>();
ts2.add(new BaseStudent("王武",29));
ts2.add(new BaseStudent("赵六",26));
ts2.add(new BaseStudent("码子",12));
System.out.println(ts2);
ts1.addAll(ts2);
System.out.println(ts1);
}
public void demo() {
ArrayList<Student> list1 = new ArrayList<>();
list1.add(new Student("张三",23));
list1.add(new Student("李四",24));
ArrayList<BaseStudent> list2 = new ArrayList<>();
list2.add(new BaseStudent("王五",23));
list2.add(new BaseStudent("赵六",24));
list1.addAll(list2);
System.out.println(list1);
}
}
class CompareByAge implements Comparator<Student>{
@Override
public int compare(Student s1, Student s2) {
int num = s2.getAge() - s1.getAge();
return num == 0 ? s2.getName().compareTo(s1.getName()) : num;
}
}
package project;
public class BaseStudent extends Student {
public BaseStudent() {
super();
}
public BaseStudent(String name, int age) {
super(name, age);
}
}
package project;
public class Student implements Comparable<Student>{
private String name;
private int age;
public Student() {
super();
}
public Student(String name, int age) {
super();
this.name = name;
this.age = age;
}
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;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + "]";
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Student other = (Student) obj;
if (age != other.age)
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
@Override
public int compareTo(Student o) {
int num = this.age - o.age; //以年龄为主要条件
return num == 0 ? this.name.compareTo(o.name) : num;
}
}