TreeMap

 

 

@AllArgsConstructor
@NoArgsConstructor
@Data
public class Student {

    private int age;
    private String name;
    private double height;

}

class Bijiaoqi implements Comparator<Student>{

    @Override
    public int compare(Student student1, Student student2) {

        //return student1.getAge()-student2.getAge();
       // return ((Double)(student1.getHeight())).compareTo((Double)(student2.getHeight()));
        return  ((String)(student1.getName())).compareTo(student2.getName());
    }
}

public class TreeMapTest {
    public static void main(String[] args) {
        TreeMap<String, Integer> treeMap = new TreeMap<>();
        treeMap.put("alili", 12);
        treeMap.put("clili", 12);
        treeMap.put("dlili", 12);
        treeMap.put("blili", 12);
        treeMap.put("alili", 12);
        System.out.println(treeMap);
        System.out.println(treeMap.size());//根据key 的值升序排列
        System.out.println("------------------");
        Bijiaoqi bijiaoqi = new Bijiaoqi();
        TreeMap<Student, String> treeMap1 = new TreeMap<>(bijiaoqi);//根据比较器的定义来决定key 是由学生的那个属性确定
        treeMap1.put(new Student(12,"azhangsan",12.22), "学生");
        treeMap1.put(new Student(13,"bzhangsan",12.22), "学生");
        treeMap1.put(new Student(14,"czhangsan",12.22), "学生");
        treeMap1.put(new Student(14,"azhangsan",12.22), "学生");
        System.out.println(treeMap1);
        System.out.println(treeMap1.size());
    }
}