TreeMap的使用和底层原理

 

package TreeMap;
import java.util.Map;
import java.util.TreeMap;

//TreeMap的使用
public class TreeMap1 {
    public static void main(String[] args) {
        Map<Integer,String> treemap1=new TreeMap<>();
        treemap1.put(20,"aa");
        treemap1.put(3,"bb");
        treemap1.put(6,"cc");
        //按照key递增的方式排序
        for(Integer key:treemap1.keySet()){
            System.out.println(key+"---"+treemap1.get(key));
        }
        Map<Emp,String> treemap2=new TreeMap<>();
        treemap2.put(new Emp(100,"张三",50000),"张三是一个好小伙");
        treemap2.put(new Emp(200,"李四",5000),"李四是一个好小伙");
        treemap2.put(new Emp(150,"王五",6000),"王五是一个好小伙");
        treemap2.put(new Emp(50,"王五",6000),"赵六是一个好小伙");
        for(Emp key:treemap2.keySet()){
            System.out.println(key+"---"+treemap2.get(key));
        }
    }
}
class Emp implements  Comparable<Emp>{//Comparable接口
    int id;
    String name;
    double salary;
    public Emp(int id,String name,double salary){
        this.id=id;
        this.name=name;
        this.salary=salary;

    }
    public String toString(){
        return "id:"+id+"name:"+name+",salary"+salary;
    }

    @Override
    public int compareTo(Emp o) {//复数小于 0等于 正数大于
        if(this.salary>o.salary){
            return 1;
        }else if(this.salary<o.salary){
            return -1;
        }else{
            if(this.id>o.id){
                return 1;
            }else if(this.id<o.id){
                return -1;
            }else{
                return 0;
            }
        }

    }
}