Map集合的使用

package cn;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class MapTest {
public static void main(String[] args) {

//创建Map集合，键对象为Integer类型，值对象为Student类型
Map<Integer,Student> stuMap=new HashMap<Integer,Student>();
stuMap.put(10, new Student(10,"张三",90));
stuMap.put(12, new Student(12,"李四",80));
stuMap.put(23, new Student(23,"王五",70));
stuMap.put(34, new Student(34,"赵六",60));

//根据键删除元素
stuMap.remove(23);

//根据键，得到值，如果键不存在，则返回null
//Student s=stuMap.get(23);
//System.out.println(s.getCode()+"  "+s.getName()+"  "+s.getGrade());

//得到键的集合
//Set<Integer> ks=stuMap.keySet();
////遍历键集合
//for(Integer key:ks){
//System.out.println("键："+key);
////根据键，得到值
//Student s=stuMap.get(key);
//System.out.println("值："+s.getCode()+"  "+s.getName()+"  "+s.getGrade());
//}

//得到Map中值的集合
Collection<Student> col=stuMap.values();
for(Student s:col){
System.out.println(s.getCode()+"  "+s.getName()+"  "+s.getGrade());
}
}

}
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