TreeMap

TreeMap一般用来快速查找数据，他的键值是不重复的，默认按照从小到大排序，键值排序通常有两种方式实现Comparable或者实现比较器Comparator.

1.创建对象

　　TreeMap map = new TreeMap()

　　TreeMap map = new TreeMap(比较器)

2.简单测试

 public class Test1 {
 public static void main(String[] args) {
  TreeMap<Integer,String> map = new TreeMap<>();
  
  map.put(3333, "3");
  map.put(1111, "1");
  map.put(2222, "2");
  map.put(7777, "7");
  map.put(4444, "4");
  map.put(6666, "6");
  map.put(5555, "5");
  
  System.out.println(map);//{1111=1, 2222=2, 3333=3, 4444=4, 5555=5, 6666=6, 7777=7}
  System.out.println(map.size());//7
  System.out.println(map.get(7777));//7
  System.out.println(map.remove(4444));//4
  System.out.println(map);//{1111=1, 2222=2, 3333=3, 5555=5, 6666=6, 7777=7}
 }
}

3.关于比较器的小例子

public class Test {
    public static void main(String[] args) {
        Point a = new Point(1,18);
        Point b = new Point(2,25);
        
        Comparator<Point> comp = new Comparator<Point>() {
            
            @Override
            public int compare(Point lhs, Point rhs) {
                return rhs.getY()-lhs.getY();
            }
        };
        
        TreeMap<Point, String> map = new TreeMap<>(comp);
        map.put(a, "1.8亿");
        map.put(b, "2.5亿");
        System.out.println(map);//{(2,25)=2.5亿, (1,18)=1.8亿}
    }
}

public class Point {
    private int x;
    private int y;
    
    public Point() {
        super();
    }

    public Point(int x, int y) {
        super();
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }

    @Override
    public String toString() {
        return "("+x+","+y+")";
    }
}