TreeMap类
package cn.sxt.collection;
import java.util.Map;
import java.util.TreeMap;
/**
* 测试TreeMap的使用
* @author Administrator
*
*/
public class TestTreeMap {
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), "李四工作不积极");
treemap2.put(new Emp(150,"王五",6000), "王五工作还不错");
treemap2.put(new Emp(50,"赵六",6000), "赵六是个开心果");
//按照key递增的方式排序
for(Emp key:treemap2.keySet()){
System.out.println(key+"---"+treemap2.get(key));
}
}
}
class Emp implements Comparable<Emp> {
int id;
String name;
double salary;
public Emp(int id, String name, double salary) {
super();
this.id = id;
this.name = name;
this.salary = salary;
}
@Override
public String toString() {
return "id:"+id+",name:"+name+",salary:"+salary;
}
@Override
public int compareTo(Emp o) { //负数：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;
}
}
}
}
运行结果：
3—bb
6—cc
20—aa
id:200,name:李四,salary:5000.0—李四工作不积极
id:50,name:赵六,salary:6000.0—赵六是个开心果
id:150,name:王五,salary:6000.0—王五工作还不错
id:100,name:张三,salary:50000.0—张三是一个好小伙
小总结
HashMap和TreeMap的不同，就是HashMap内部没有排序，而TreeMap实现了Comparable接口，内部按照一定的规则排序了。
