关于#for#的问题，如何解决？

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  • java
       HashMap<String,HashMap<String,Integer>>studentname=new HashMap<>();
  HashMap<String,Integer>mark1=new HashMap<>();
  mark1.put("语文", 11);
  mark1.put("数学", 22);
  mark1.put("英语", 33);
  HashMap<String,Integer>mark2=new HashMap<>();
  mark2.put("语文", 100);
  mark2.put("数学", 100);
  mark2.put("物理", 100);
  HashMap<String,Integer>mark3=new HashMap<>();
  mark3.put("语文", 80);
  mark3.put("物理", 40);
  mark3.put("英语", 60);
  studentname.put("珈乐", mark1);
  studentname.put("贝拉", mark2);
  studentname.put("嘉然", mark3);
   for (String student : studentname.keySet()) {//遍历大的哈希map
       System.out.print("\n"+student);
          for (String course: studentname.get(student).keySet()) {//遍历小的哈希map     
          }
           }
   System.out.print("请输入您想查询的科目");
   Scanner in=new Scanner(System.in);
   String b=in.next();
   int x=0;
   String g[]={"语文","数学","英语","物理"};
   for(String student:studentname.keySet()) {//遍历大哈希map里的学生名字
       for(String course:studentname.get(student).keySet()) {//遍历小哈希map里面科目的名字
           if(course==b)
           {
            System.out.print(student);
            System.out.print(studentname.get(student).get(b)+"\n");
           }     
       }
        }

string 比较 用 equals

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