Interface Comparator<T>

對任意類型集合對象進行整體排序，排序時將此接口的實現傳遞給Collections.sort方法或者Arrays.sort方法排序.
實現int compare(T o1, T o2)方法。

單一條件排序:

舉例:

List<Student> stus = new ArrayList<Student>(){{add(new Student("張三", 30)); add(new Student("李四", 20)); add(new Student("王五", 60)); }};// 1.對學生集合按年齡進行排序Collections.sort(stus, new Comparator<Student>() {@Overridepublic 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.對學生集合按姓名首字母排序Comparator comparator = Collator.getInstance(Locale.CHINA);Collections.sort(stus, new Comparator<Student>() {@Overridepublic int compare(Student s1, Student s2) {return comparator.compare(s1.getName(), s2.getName());}});// 輸出結果...

注: 還可以使用lambda表達式簡化代碼, 前提是JDK8開發環境, 如下:

List<Student> stus = new ArrayList<Student>(){{add(new Student("張三", 30)); add(new Student("李四", 20)); add(new Student("王五", 60)); }};//對學生集合按年齡進行排序Collections.sort(stus, (s1,s2)->(s1.getAge()-s2.getAge()));

lambda表達式是JDK8新特性之一, 允許你通過表達式來代替功能接口; 細節請自行百度… 我也是剛接觸, 啊哈哈, 不熟悉,諒解諒解

多條件排序:

舉例:

List<Student> stus = new ArrayList<Student>(){{add(new Student("張三", 30, 1)); add(new Student("李四", 20, 2)); add(new Student("王五", 40, 3)); add(new Student("趙六", 30, 4)); add(new Student("陳七", 40, 5)); add(new Student("周八", 20, 6)); }};Collections.sort(stus,new Comparator<Student>() {@Overridepublic int compare(Student s1, Student s2) {int flag;// 首選按年齡升序排序flag = s1.getAge()-s2.getAge();if(flag==0){// 再按學號升序排序flag = s1.getNum()-s2.getNum();}return flag;}});System.out.println("年齡 學號 姓名 ");for(Student s : stus){System.out.println(s.getAge()+" "+s.getNum()+" "+s.getName());}

輸出結果:

自定義條件排序

String[] order = {"語文","數學","英語","物理","化學","生物","政治","歷史","地理","總分"};final List<String> definedOrder = Arrays.asList(order);List<String> list = new ArrayList<String>(){{add("總分");add("英語");add("政治");add("總分");add("數學");}};Collections.sort(list,new Comparator<String>() {@Overridepublic 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表達式簡化代碼:

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

輸出結果:

總結

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