Set集合用法

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性质

底层采用哈希表算法，无序不可重复

数组去重

    public static String[] removeRepeat(String[] array){
		Set<String> set = new HashSet<>();
		for(int i = 0; i < array.length; i++){
			set.add(array[i]);
		}
		String[] arr = set.toArray(new String[set.size()]);
		return arr;
	}
	
	public static void main(String[] args) {
		String[] arr = {"java","java","C++","python"};
		String[] arr2 = removeRepeat(arr);
		System.out.println(Arrays.toString(arr2));
	}

集合去重

        List<String> list = new ArrayList<>();
		list.add("aa");
		list.add("aa");
		list.add("bb");
		list.add("cc");
		list.add("cc");
		System.out.println("去重前list:"+list);
		Set<String> set2= new HashSet<>();
		set2.addAll(list);
		System.out.println("set2:"+set2);
		list.clear();
		list.addAll(set2);
		System.out.println("去重后list:"+list);

TreeSet自动排序

实体类必须实现Comparable接口并重写CompareTo方法，编写排序规则（升序、降序）

public class SetTest {

	public static void main(String[] args) {

		Set<Person> set3 = new TreeSet<>();
		set3.add(new Person("Daniel",22));
		set3.add(new Person("Eddie",21));
		set3.add(new Person("Jesska",20));
		System.out.println(set3);

	}
}

class Person implements Comparable<Person>{
	
	String name;
	int age;
	
	public Person() {
		super();
		// TODO Auto-generated constructor stub
	}
	
	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	
	
	public String getName() {
		return name;
	}

	public int getAge() {
		return age;
	}

	@Override
	public int compareTo(Person arg0) {
		return this.age - arg0.getAge();
	}
}