comparable接口实现排序_java compareto方法怎么排序的

Interface Comparator<T>

对任意类型集合对象进行整体排序，排序时将此接口的实现传递给Collections.sort方法或者Arrays.sort方法排序.
实现int compare(T o1, T o2)方法。

单一条件排序:

举例:

		List<Student> stus = new ArrayList<Student>(){
			{
				add(new Student("张三", 30));	
				add(new Student("李四", 20));	
				add(new Student("王五", 60));	
			}
		};
		// 1.对学生集合按年龄进行排序
		Collections.sort(stus, new Comparator<Student>() {

			@Override
			public int compare(Student s1, Student s2) {
				// 升序
				//return s1.getAge()-s2.getAge();
				return s1.getAge().compareTo(s2.getAge());
				// 降序
				// return s2.getAge()-s1.getAge();
				// return s2.getAge().compareTo(s1.getAge());
			}
		});
		
		// 2.对学生集合按姓名首字母排序
		Comparator comparator = Collator.getInstance(Locale.CHINA);
		Collections.sort(stus, new Comparator<Student>() {
		
			@Override
			public int compare(Student s1, Student s2) {
				return comparator.compare(s1.getName(), s2.getName());
			}
		
		});
		
		// 输出结果
		...
		

注: 还可以使用lambda表达式简化代码, 前提是JDK8开发环境, 如下:

		List<Student> stus = new ArrayList<Student>(){
			{
				add(new Student("张三", 30));	
				add(new Student("李四", 20));	
				add(new Student("王五", 60));	
			}
		};
		//对学生集合按年龄进行排序
		Collections.sort(stus, (s1,s2)->(s1.getAge()-s2.getAge()));

lambda表达式是JDK8新特性之一, 允许你通过表达式来代替功能接口; 细节请自行百度… 我也是刚接触, 啊哈哈, 不熟悉,谅解谅解

多条件排序:

举例:

		List<Student> stus = new ArrayList<Student>(){
			{
				add(new Student("张三", 30, 1));	
				add(new Student("李四", 20, 2));	
				add(new Student("王五", 40, 3));	
				add(new Student("赵六", 30, 4));	
				add(new Student("陈七", 40, 5));	
				add(new Student("周八", 20, 6));	
			}
		};
		Collections.sort(stus,new Comparator<Student>() {

			@Override
			public int compare(Student s1, Student s2) {
				int flag;
				// 首选按年龄升序排序
				flag = s1.getAge()-s2.getAge();
				if(flag==0){
					// 再按学号升序排序
					flag = s1.getNum()-s2.getNum();
				}
				return flag;
			}
		});
		
		System.out.println("年龄       学号       姓名  ");
		for(Student s : stus){
			System.out.println(s.getAge()+"   "+s.getNum()+"   "+s.getName());
		}

输出结果:

自定义条件排序

		String[] order = {"语文","数学","英语","物理","化学","生物","政治","历史","地理","总分"};
		final List<String> definedOrder = Arrays.asList(order);
		List<String> list = new ArrayList<String>(){
			{
				add("总分");
				add("英语");
				add("政治");
				add("总分");
				add("数学");
			}
		};
		Collections.sort(list,new Comparator<String>() {

			@Override
			public int compare(String o1, String o2) {
				int io1 = definedOrder .indexOf(o1);
				int io2 = definedOrder .indexOf(o2);
				return io1-io2;
			}
		});
		
		for(String s:list){
			System.out.print(s+"   ");
		}

使用lambda表达式简化代码:

Collections.sort(list, (o1, o2)->(definedOrder .indexOf(o1)-definedOrder .indexOf(o2)));

输出结果:

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