TreeSet 的使用练习
代码一：
package thirteendemo;
/*
* MyDate类包含:
private成员变量month,day,year；并为每一个属性定义 getter, setter 方法；
*/
public class MyDate {
private int day;
private int month;
private int year;
public int getDay() {
return day;
}
public void setDay(int day) {
this.day = day;
}
public int getMonth() {
return month;
}
public void setMonth(int month) {
this.month = month;
}
public int getYear() {
return year;
}
public void setYear(int year) {
this.year = year;
}
public MyDate(int day, int month, int year) {
super();
this.day = day;
this.month = month;
this.year = year;
}
@Override
public String toString() {
return "MyDate [day=" + day + ", month=" + month + ", year=" + year
+ "]";
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + day;
result = prime * result + month;
result = prime * result + year;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
MyDate other = (MyDate) obj;
if (day != other.day)
return false;
if (month != other.month)
return false;
if (year != other.year)
return false;
return true;
}
}
代码二：
package thirteendemo;
/*
* 定义一个Employee类，
该类包含：private成员变量name,age,birthday，其中 birthday 为 MyDate 类的对象；
并为每一个属性定义 getter, setter 方法；
并重写 toString 方法输出 name, age, birthday
*/
public class Employee implements Comparable{
private String name;
private int age;
private MyDate birthday;
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 MyDate getBirthday() {
return birthday;
}
public void setBirthday(MyDate birthday) {
this.birthday = birthday;
}
public Employee(String name, int age, MyDate birthday) {
super();
this.name = name;
this.age = age;
this.birthday = birthday;
}
@Override
public String toString() {
return "Employee [name=" + name + ", age=" + age + ", birthday="
+ birthday + "]";
}
@Override
public int compareTo(Object o) {
if(o instanceof Employee){
Employee e = (Employee)o;
return this.name.compareTo(e.name);
}
return 0;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result
+ ((birthday == null) ? 0 : birthday.hashCode());
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;
Employee other = (Employee) obj;
if (age != other.age)
return false;
if (birthday == null) {
if (other.birthday != null)
return false;
} else if (!birthday.equals(other.birthday))
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
}
代码三：
package thirteendemo;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;
import org.junit.Test;
/*
* 创建该类的 5 个对象，并把这些对象放入 TreeSet 集合中（下一章：TreeSet 需使用泛型来定义）
分别按以下两种方式对集合中的元素进行排序，并遍历输出：
1). 使Employee 实现 Comparable 接口，并按 name 排序
2). 创建 TreeSet 时传入 Comparator对象，按生日日期的先后排序。
提示：Employee类是否需要重写equals()方法？MyDate类呢？
*/
public class TestEmployee {
//定制排序：创建 TreeSet 时传入 Comparator对象，按生日日期的先后排序。
@Test
public void test2(){
Comparator com = new Comparator(){
@Override
public int compare(Object o1, Object o2) {
if(o1 instanceof Employee1 && o2 instanceof Employee1){
Employee1 e1 = (Employee1)o1;
Employee1 e2 = (Employee1)o2;
MyDate birth1 = e1.getBirthday();
MyDate birth2 = e2.getBirthday();
if(birth1.getYear() != birth2.getYear()){
return birth1.getYear() - birth2.getYear();
}else{
if(birth1.getMonth() != birth2.getMonth()){
return birth1.getMonth() - birth2.getMonth();
}else{
return birth1.getDay() - birth2.getDay();
}
}
}
return 0;
}
};
TreeSet set = new TreeSet(com);
Employee1 e1 = new Employee1("刘德华", 55, new MyDate(4, 12, 1976));
Employee1 e2 = new Employee1("郭富城", 43, new MyDate(7, 3, 1954));
Employee1 e3 = new Employee1("张学友", 33, new MyDate(9, 12, 1954));
Employee1 e4 = new Employee1("黎明", 54, new MyDate(12, 3, 1954));
Employee1 e5 = new Employee1("李敏镐", 65, new MyDate(4, 21, 1945));
set.add(e1);
set.add(e2);
set.add(e3);
set.add(e4);
set.add(e5);
Iterator i = set.iterator();
while(i.hasNext()){
System.out.println(i.next());
}
}
//自然排序： 使Employee 实现 Comparable 接口，并按 name 排序
@Test
public void test1(){
Employee e1 = new Employee("刘德华", 55, new MyDate(4, 12, 1976));
Employee e2 = new Employee("郭富城", 43, new MyDate(7, 3, 1965));
Employee e3 = new Employee("张学友", 33, new MyDate(9, 12, 1954));
Employee e4 = new Employee("黎明", 54, new MyDate(12, 2, 1967));
Employee e5 = new Employee("李敏镐", 65, new MyDate(4, 21, 1945));
// Employee e6 = new Employee("李敏镐", 63, new MyDate(4, 21, 1945));
TreeSet set = new TreeSet();
set.add(e1);
set.add(e2);
set.add(e3);
set.add(e4);
set.add(e5);
// set.add(e6);
Iterator i = set.iterator();
while(i.hasNext()){
System.out.println(i.next());
}
}
}
代码四：
package thirteendemo;
/*
* 定义一个Employee类，
该类包含：private成员变量name,age,birthday，其中 birthday 为 MyDate 类的对象；
并为每一个属性定义 getter, setter 方法；
并重写 toString 方法输出 name, age, birthday
*/
public class Employee1 {
private String name;
private int age;
private MyDate birthday;
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 MyDate getBirthday() {
return birthday;
}
public void setBirthday(MyDate birthday) {
this.birthday = birthday;
}
public Employee1(String name, int age, MyDate birthday) {
super();
this.name = name;
this.age = age;
this.birthday = birthday;
}
@Override
public String toString() {
return "Employee [name=" + name + ", age=" + age + ", birthday="
+ birthday + "]";
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result
+ ((birthday == null) ? 0 : birthday.hashCode());
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;
Employee1 other = (Employee1) obj;
if (age != other.age)
return false;
if (birthday == null) {
if (other.birthday != null)
return false;
} else if (!birthday.equals(other.birthday))
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
}
韧桂 2020-01-02