abstract class Student
{
      String name;
    String type;
    float score;
    String level;
    abstract String GetName();
    abstract String GetType();
    abstract float GetScore();
    abstract String GetLevel();
 };
 interface I1{
    public String GetLevel();
 
 
 
 
 }
 class UnderI1 implements I1
 {         
            String GetLevel(float score){
        if(this.score>=85&&this.score<100)
            level = "excellent";
        if(this.score<85&&this.score>=75)
            level = "good";
        if(this.score<75&&this.score>=65)
            level = "middle";
        if(this.score<65&&this.score>=60)
            level = "poor";
        if(this.score<60)
            level = "fail";
   
   
    }
 };
 class PostI1 implements I1

 {
        String GetLevel(float score){
        if(this.score>=90&&this.score<=100)
            level = "excellent";
        if(this.score<90&&this.score>=80)
            level = "good";
        if(this.score<80&&this.score>=70)
            level = "middle";
        if(this.score<70&&this.score>=60)
            level = "poor";
        if(this.score<60)
            level = "fail";
   
   
    }
 };
class Undergraduate extends Student{
     
    String GetName(String x){
    this.name = x;

   
    }
    String GetType(String y){
    this.type = y;
   
    }
    float GetScore(float a){
        this.score = a;
   
   
    }
   
   
    }
    public String toString(){
        return "Name:"+name+"\nType:"+type+"\nScore:"
        +score+"\nLevel:"+level+"\n";
   
   
   
   
   
    }
};
class Postgraduate extends Student
{     
     

    String GetName(String x){
        this.name = x;
   
    }
    String GetType(String y){
        this.type = y;
    }
    String GetScore(float a){
        this.score = a;
   
    }
   
    public String toString(){
        return "Name:"+name+"\nType:"+type+"\nScore:"
        +score+"\nLevel:"+level+"\n";
   
   
    }
};

public class StudentDemo
{
    public static void main(String[] args)
    {
        Undergraduate a = new Undergraduate();
        I1 c = new UnderI1();

        a.GetName("Tom Smith");
        a.GetType("Undergraduate");
        a.GetScore(85.3f);
        a.level = c.GetLevel(a.score);
        System.out.println("As follows,this is some exam information of an undergraduate");
        a.toString();
        
        Postgraduate b = new Postgraduate();
        c = new PostI1();
        b.GetName("Jerry Zhang");
        b.GetType("Postgraduate");
        b.GetScore(91.3f);
        b.level = c.GetLevel(b.score);
        System.out.println("As follows,this is some exam information of a postgraduate");
        b.toString();
    };
};
//我不知道为什么toString（）没法用，求解！！！！！！！！！小弟感激不尽

模糊

请帮我看看我传的输出信息

搞清楚抽像类与接口的概念后,再重新设计你的类吧, 你的程序可以再简洁些的
get 和set方法不能混合在一起: get方法没有参数,但要有返回类型, set方法有一个参数。没有返回类型

顶楼上

给你调试了一下程序你实现接口中的方法不应该带参数，另外你的继承也出现了问题，还有get()和set()，建议您以后再写代码的时候写上注释，这是一个优秀的程序员的必备！其他不明白的地方可以查询API文档