set集合的基本特点,set集合底层去重原理,集合怎么进行排序

package com.xiaolei.set; import java.util.HashMap; import java.util.HashSet; import java.util.Iterator; import java.util.Map; /** * set集合底层去重原理 * 1.hashset底层去重,与hashCode、equals方法相关 * 2.是优先对比hashCode值在对比equals值，当hashCode值相同，并且equals返回的值是true，则判定为重复元素 * 2.1 hashCode值不相同，就不会调用equals方法进行比较了 * 2.2 hashCode值相同，就调用equals方法 * @author 肖磊 * */ public class Demo2 { public static void main(String[] args) { HashSet<Person> set=new HashSet<>(); //增加 //方法一 // set.add(new Person("小王", 10, 100)); // set.add(new Person("小王", 10, 100)); // set.add(new Person("小李", 11, 200)); // set.add(new Person("小黑", 12, 300)); // set.add(new Person("小哈", 13, 400)); // set.add(new Person("老李", 14, 500)); //方法二 Person p1=new Person("小王", 10, 100); Person p2=new Person("小王", 10, 100); Person p3=new Person("小李", 11, 200); Person p4=new Person("小黑", 12, 300); Person p5=new Person("小哈", 13, 400); Person p6=new Person("老李", 14, 500); set.add(p1); set.add(p2); set.add(p3); set.add(p4); set.add(p5); set.add(p6); System.out.println(set.size()); p6.setName("老二");//获取p6里面的name属性把它修改成括号里的内容;只要它调用了这个方法不管它在传给set的前面或后面调用都修改成功 for (Person per : set) { System.out.println(per); } //一下实验调用下面xxx的方法返回的是xxx里的map.put("a", 1);括号里面的返回值 // Map m=new HashMap<>(); // xxx(m); // System.out.println(m); } // public static void xxx(Map map) { // map.put("a", 1); // } } class Person implements Comparable<Person>{//使用treeset集合进行排序必须实现Comparable接口 private String name; private int age; private float salary; 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 float getSalary() { return salary; } public void setSalary(float salary) { this.salary = salary; } public Person(String name, int age, float salary) { super(); this.name = name; this.age = age; this.salary = salary; } @Override public String toString() { return "Person [name=" + name + ", age=" + age + ", salary=" + salary + "]"; } public Person() { super(); } @Override public int hashCode() { System.out.println("-----------hashCode-------------"); final int prime = 31; int result = 1; result = prime * result + age; result = prime * result + ((name == null) ? 0 : name.hashCode()); result = prime * result + Float.floatToIntBits(salary); return result;//把返回的值改成1和equals返回的值改成true就会输出重复的 } @Override public boolean equals(Object obj) {//如果发现重复的就会运行此方法 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 (name == null) { if (other.name != null) return false; } else if (!name.equals(other.name)) return false; if (Float.floatToIntBits(salary) != Float.floatToIntBits(other.salary)) return false; return true; } @Override public int compareTo(Person o) {//通过name的首字母拼音进行排序所有.name和.getname(this.name.compareTo(o.getName()) // TODO Auto-generated method stub return (int) (this.salary-o.salary);//按照工资进行排序return this.salary-o.salary; } }