自定义类型在Set容器里

一、子定义Person类在Set容器里的唯一值条件

1.自定义Person类

2.重写hashCode() 与 equals()函数

public class Person {private String id;private String name;private int age; public Person(){}public Person(String id, String name, int age) {super();this.id = id;this.name = name;this.age = age;}@Override//确定自定义类型的hashCode的值public int hashCode() {System.out.println("hashcode");final int prime = 31;int result = 1;result = prime * result + age;result = prime * result + ((id == null) ? 0 : id.hashCode());result = prime * result + ((name == null) ? 0 : name.hashCode());return result;}@Override//确定自定类型的比较方式： 这里是如果年龄、id、姓名都相等的话就是相等//没有重写该方法的情况，系统默认使用Object的equals()方法 ，比较的是地址public boolean equals(Object obj) {System.out.println("equals");if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;Person other = (Person) obj;if (age != other.age)return false;if (id == null) {if (other.id != null)return false;} else if (!id.equals(other.id))return false;if (name == null) {if (other.name != null)return false;} else if (!name.equals(other.name))return false;return true;}public String getId() {return id;}public void setId(String id) {this.id = id;}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;}}

在容器中添加自定义的类

import java.util.HashSet;import java.util.Set;public class Test {public static void main(String[] args) {Set<Person> set = new HashSet<Person>();set.add(new Person("1001","xiaolizi",20));   // 1set.add(new Person("1002","xiaoming",22));set.add(new Person("1002","xiaoming",22));  // 3System.out.println(set.size());}}

ps:  1和3处使用了Person类的hashCode();方法后，他们的hashCode值相同

使用equals()方法进行比较；  确定 1和3相同;

结果

二、自定义类型在TreeSet的排序方法

1.前面步骤相同

2.内部比较，实现Comparable 接口，重写方法comparaTo

public class Student implements Comparable<Student>{private String name;private int age;public Student() {}public Student(String name, int age) {super();this.name = name;this.age = age;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + age;result = prime * result + ((name == null) ? 0 : name.hashCode());return result;}@Overridepublic String toString() {return "Student [name=" + name + ", age=" + age + "]";}/* * 实现了Comparable接口，重写了compareTo方法  ;来实现内部比较 * 定义该类在Set里面的排序方式 */@Overridepublic int compareTo(Student o) {//按照age来排序return this.age - o.age;  // 小于、等于或大于时，则分别返回负整数、零或正整数。 }@Overridepublic 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;}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;}}

测试类

import java.util.Set;import java.util.TreeSet;public class TestStu {public static void main(String[] args) {Set<Student> set = new TreeSet<Student>();set.add(new Student("zhangsan",12));set.add(new Student("lisi",10));set.add(new Student("zhangsan",12));System.out.println("容器内元素"+set.size());System.out.println(set);}}

执行结果：