方法一：內部類實現comparator介面

程式碼演示

import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

class B{
	String name;
	String date;
}
public class Test {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		B a [] = new B[
 
n]; //宣告一個物件陣列
		for (int i = 0; i < n; i++) {
			a[i] = new B(); //分配記憶體等操作
			a[i].name = in.next();
			a[i].date = in.next();
		}
		//從小到大大排序
		Arrays.sort(a, new Comparator<B>() { //內部類

			@Override
			public int compare(B o1, B o2) {
				return o1.date.compareTo(o2.date);
			}
			
		});
		
		for
 
 (int i = 0; i < n; i++) { //輸出
			System.out.print(a[i].name+" ");
			System.out.println(a[i].date);
		}
	}
}

輸入

5
John 2001/05/12
Tom 1814/09/06
Ann 2121/01/30
James 1814/09/05
Steve 1967/11/20

結果

James 1814/09/05
Tom 1814/09/06
Steve 1967/11/20
John 2001/05/12
Ann 2121/01/30

方法二：實現comparable介面

程式碼演示

import java.util.Arrays;
 

import java.util.Comparator;
import java.util.Scanner;

class A implements Comparable<A>{ //實現comparable介面，複寫comparato方法
	String name;
	String date;
	@Override
	public int compareTo(A a) { 
		if (this.date.compareTo(a.date) == -1) 
			return 1;
		else 
			return -1;
	}
}
public class Test {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		A a [] = new A[n];
		for (int i = 0; i < n; i++) {
			a[i] = new A();
			a[i].name = in.next();
			a[i].date = in.next();
		}
		Arrays.sort(a);//從大到小排序
		
		for (int i = 0; i < n; i++) {
			System.out.print(a[i].name+" ");
			System.out.println(a[i].date);
		}
	}
}

輸入

5
John 2001/05/12
Tom 1814/09/06
Ann 2121/01/30
James 1814/09/05
Steve 1967/11/20

結果

Ann 2121/01/30
John 2001/05/12
Steve 1967/11/20
Tom 1814/09/06
James 1814/09/05