java排序算法完整版

调用java类排序有三种情况：（这里都以int排序）

<1>：直接对数组排序：

 

import java.util.Arrays;

public class SortArray {

	public static void main(String[] args) {
		int []arr1 = {1,9,6,2,7,5,4,8,3};
		int []arr2 = {1,9,6,2,7,5,4,8,3};
		sort(arr1);
		sort(arr2,0,5);
	}
	
	//按升序对数组中的[fromIndex,toIndex)进行排序（即从fromIndex--(toIndex-1)的数据）
	public static void sort(int[] arr,int fromIndex,int toIndex){
		Arrays.sort(arr, fromIndex, toIndex);
		System.out.println("Arrays.sort(arr, 0, 5):");
		for(int i=0;i<arr.length;i++){
			System.out.print(arr[i]+" ");
		}
		System.out.println();
	}
	
	//按升序对数组全部数据排序
	public static void sort(int[] arr){
		Arrays.sort(arr);
		System.out.println("Arrays.sort(arr):");
		for(int i=0;i<arr.length;i++){
			System.out.print(arr[i]+" ");
		}
		System.out.println();
	}

}

 

 

<2>:对List进行排序  本身实现Comparable接口

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class CollectionsOfSort {
	public static void main(String[] args) {
		List<Stu> list = new ArrayList<Stu>();
		list.add(new Stu(1));
		list.add(new Stu(9));
		list.add(new Stu(6));
		list.add(new Stu(2));
		list.add(new Stu(7));

		sort(list);

	}

	public static void sort(List<Stu> list) {
		Collections.sort(list);
		for (int i = 0; i < list.size(); i++) {
			System.out.println(list.get(i).id + " ");
		}
	}
}

class Stu implements Comparable<Stu> {
	Integer id;

	public Stu(int id) {
		this.id = id;
	}

	@Override
	public int compareTo(Stu stu) {
		return this.id.compareTo(stu.id);
		// return stu.id.compareTo(this.id);//降序排列
	}
}

 

 

<3>:对List进行排序  另写程序实现Comparator 接口

 

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class CollectionsOfSort {
	public static void main(String[] args) {
		List<Person> listPerson =new ArrayList<Person>();
		listPerson.add(new Person(1));
		listPerson.add(new Person(9));
		listPerson.add(new Person(6));
		listPerson.add(new Person(2));
		listPerson.add(new Person(7));
		sort(listPerson, new SortPerson());

	}

	public static void sort(List<Person> list, Comparator<Person> c) {
		Collections.sort(list, c);
		for (int i = 0; i < list.size(); i++) {
			System.out.print(list.get(i).age + " ");
		}
	}

}

class SortPerson implements Comparator<Person> {
	@Override
	public int compare(Person p1, Person p2) {
		return p1.age.compareTo(p2.age);
		// return p2.age.compareTo(p2.age);//降序
	}

}

class Person {
	public Person(int age) {
		this.age = age;
	}

	Integer age;
}