常用功能
- public static < T > bollean addAll(Collection< T > c,T…elements):往集合中添加元素
- public static void shutffle(List<?>list):打乱顺序
- public static < T > sort(List<?>list):按默认规则升序排序
- public static < T > sort(List<?>list,Comparator<? Super T>):按指定规则排序
对已有类型排序
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| public static void main(String[] args) { ArrayList<Integer> list = new ArrayList<>(); list.add(2); list.add(1); Collections.sort(list); Collections.sort(list, new Comparator<Integer>() { @Override public int compare(Integer o1, Integer o2) { return o1-o2; } }); }
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对自定义类型排序:对Comparable重写定义排序规则:this-参数(升序)
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| public class Person implements Comparable{ private String name; private int age;
@Override public int compareTo(Object o) { return this.getAge() - ((Person)o).getAge(); } }
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| Collections.sort(list, new Comparator<Person>() { @Override public int compare(Person o1, Person o2) { int result = o1.getAge() - o2.getAge(); if(result == 0){ result = o1.getName().charAt(0) - o2.getName().charAt(0); } return result; } });
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