Collections&Comparator&Comparable类API

//	向集合中添加元素，可以是泛型的集合形式的，也可以是T的可变参数（多个T类型数据，或者T类型数组）
public static <T> boolean AddAll(Collection<T> c, T... elements)

//	将列表乱序
public static shuffle(List<?> list)

//	将列表按照默认规则排序
public static <T> void sort(List<T> list)

//	将列表按照给定规则排序
public static <T> void sort(List<T> list, Comparator<? super T>)

//	Comparator排序需要实现的方法，o1-o2是升序；o2-o1是降序
public int compare(String o1, String o2)

使用Comparator排序

//	一个对象
public class Student() {
	private String name;
	private int age;
	
	public Studnet() {
	}
	
	public Student(String name, int age) {
		this.name = name;
		this.age = age;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public String getName() {
		return name;
	}
	
	public void setAge(int age) {
		this.age = age;
	}
	
	public int getAge() {
		return age;
	}
	
	@Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}
//	测试
//	o1 - o2升序;o2 - o1降序
public void Demo() {
	public static void main(String[] args) {
		List students = new ArrayList<String>();
		students.add(new Student("StudentA", 10));
		students.add(new Student("StudentD", 40));
		students.add(new Student("StudentC", 30));
		students.add(new Student("StudentE", 50));
		students.add(new Student("StudentB", 20));
		Collections.sort(students， Comparator<Student>() {
			@Override
			public int compare(Student o1, Student o2) {
				return o2.getAge() - o1.getAge();
			}
		});
		for(Student student : students) {
			System.out.println(student);
		}
		//	Student{name='StudentE', age=50}
		//	Student{name='StudentD', age=40}
		//	Student{name='StudentC', age=30}
		//	Student{name='StudentB', age=20}
		//	Student{name='StudentA', age=10}
	}
}

使用Comparable排序

//	一个对象
public class Student() implements Comparable<Student>{
	private String name;
	private int age;
	
	public Studnet() {
	}
	
	public Student(String name, int age) {
		this.name = name;
		this.age = age;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public String getName() {
		return name;
	}
	
	public void setAge(int age) {
		this.age = age;
	}
	
	public int getAge() {
		return age;
	}
	
	@Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

	@Override
	public int compareTo(String o) {
		//	this-o是升序
		//	o-this是降序
		return this.age - o.age;
	}
}
//	测试
public void Demo() {
	public static void main(String[] args) {
		List students = new ArrayList<String>();
		students.add(new Student("StudentA", 10));
		students.add(new Student("StudentD", 40));
		students.add(new Student("StudentC", 30));
		students.add(new Student("StudentE", 50));
		students.add(new Student("StudentB", 20));
		Collections.sort(students);
		for(Student student : students) {
			System.out.println(student);
		}
		//	Student{name='StudentE', age=50}
		//	Student{name='StudentD', age=40}
		//	Student{name='StudentC', age=30}
		//	Student{name='StudentB', age=20}
		//	Student{name='StudentA', age=10}
	}
}

本文地址：https://blog.csdn.net/fytvewrewr/article/details/109828104