重写comparater比较器

TreeSet

能自动对对象进行排序，但是一般需要在类中重写比较方法
比较器介绍

在类中实现Comparable接口，并重写compareTo方法

排序对象类

package typing.overridecompare;

public class Person  implements Comparable<Person>{
	private String name;
	private int age;
	
	Person() {
		
	}
	
	Person(String name, int age) {
		this.name = name;
		this.age = age;
	}
	
	public String toString() {
		return "[name:" + name + ",age:" + age + "]";
	}
	
	public String getName() {
		return name;
	}
	
	public int getAge() {
		return age;
	}

	@Override
	public int compareTo(Person person) {
                // 先以年龄进行排序，再以姓名长度进行排序
		int num = this.getAge() - person.getAge();
		if (num==0) {
			num = this.getName().length() - person.getName().length();
		}
		
		return num;
		
	}
}

创建TreeSet对象并添加Person对象自动排序

package typing.overridecompare;

import java.util.Random;
import java.util.TreeSet;

public class OverrideCompareTo {
	private TreeSet<Integer> treeint;
	private TreeSet<Person> treeperson;
	
	public void treeInt() {
		treeint = new TreeSet<Integer>();
		Random r = new Random();
		for (int i = 0; i < 10; i ++)
			treeint.add(r.nextInt(100));
		System.out.println(treeint);
	}
	
	public void treePerson() {
		treeperson = new TreeSet<Person>();
		treeperson.add(new Person("ali",20));
		treeperson.add(new Person("aiya",16));
		treeperson.add(new Person("bob", 16));
		treeperson.add(new Person("boer", 21));
		treeperson.add(new Person("lobo",15));
		System.out.println(treeperson);
	}

}

测试类

                OverrideCompareTo compare = new OverrideCompareTo();
		compare.treePerson();//输出结果：[[name:lobo,age:15], [name:bob,age:16], [name:aiya,age:16], [name:ali,age:20], [name:boer,age:21]]

自定义比较器，在比较器中实现，需要实现Comparator接口并重写compare方法

自定义比较器类

package typing.overridecompare;

import java.util.Comparator;

public class CharCompare implements Comparator<Character>{
	
	@Override
	public int compare(Character c1, Character c2) {
		int num = c1 -c2;
		if (num == 0)
			num = 1;
		return num;// 以字符串的ascll顺序进行排序
		
	}

}

测试类

TreeSet<Character> charset = new TreeSet<Character>(new CharCompare());// 在声明TreeSet时传入自定义比较器对象
		Scanner input = new Scanner(System.in);
		String line = input.nextLine();
		char[] arr = line.toCharArray();
		for (char ch:arr)
			charset.add(ch);
		System.out.println(charset);
// 输入abbcba,输出aabbbc