import java.util.Scanner;
    public class ScoreTest{
        public static void main(String[] args){
            Scanner reader=new Scanner(System.in);
            double score[];
            int n;
            System.out.println("您要输入多少个学生的成绩");
            n=reader.nextInt();
            if(n<=0)
              System.out.printfln("个数错误!");
                 else
              score=new double[n];
                             for(int i=0;i<n;i++){
                                   System.out.print("请输入第"+(i+1)"个童鞋的成绩:");
                                      score[i]=reader.nextDouble();
                }
              Info.showInfo(n,score);
                           
            
    }
    class Info{
        public void showInfo(int n,double score[]){
                    Scanner reader=new Scanner(System.in);
            System.out.println("您想查找第几个童鞋的成绩?");
              int index=reader.nextInt();
                if(index>0&&index<=n)
                System.out.printfln("第"+index+"个童鞋的成绩是"+score[index+1]);
                else
                 System.out.println("对不起，您输入的数字有误!");
                    }


    }

怎么没有人啊，救命啊

System.out.printfln("第"+index+"个童鞋的成绩是"+score[index+1]);
好像是println()的，打多了一个f。

System.out.print("请输入第"+(i+1)"个童鞋的成绩:");
("请输入第"+(i+1)+"个童鞋的成绩:");
好像少了一个连接符号+

package test;

import java.util.Scanner;

public class ScoreTest {
    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        double score[] = null;
        int n;
        System.out.println("您要输入多少个学生的成绩");
        n = reader.nextInt();
        if (n <= 0)
            System.out.println("个数错误!");
        else
            score = new double[n];
        for (int i = 0; i < n; i++) {
            System.out.print("请输入第" + (i + 1) + "个童鞋的成绩:");
            score[i] = reader.nextDouble();
        }
        Info.showInfo(n, score);

    }

    static class Info {
        public static void showInfo(int n, double score[]) {
            Scanner reader = new Scanner(System.in);
            System.out.println("您想查找第几个童鞋的成绩?");
            int index = reader.nextInt();
            if (index > 0 && index <= n)
                System.out.println("第" + index + "个童鞋的成绩是" + score[index + 1]);
            else
                System.out.println("对不起，您输入的数字有误!");
        }
    }

}

试试。不要用Tab键，用空格键。。。

好像是静态的问题。

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        double score[];
        int n;
        System.out.println("您要输入多少个学生的成绩");
        n = reader.nextInt();
        if (n <= 0) {
            System.out.println("个数错误!");
        } else {
            score = new double[n];
            for (int i = 0; i < n; i++) {
                System.out.print("请输入第" + (i + 1) + "个童鞋的成绩:");
                score[i] = reader.nextDouble();
            }
            showInfo(n, score);
        }
       


    }

    public static void showInfo(int n, double score[]) {
        Scanner reader = new Scanner(System.in);
        System.out.println("您想查找第几个童鞋的成绩?");
        int index = reader.nextInt();
        if (index > 0 && index <= n)
            System.out.println("第" + index + "个童鞋的成绩是" + score[index - 1]);
        else
            System.out.println("对不起，您输入的数字有误!");
    }

import java.util.Scanner;
    public class ScoreTest{
        public static void main(String[] args){
            Scanner reader=new Scanner(System.in);
            double score[];
            int n;
            System.out.println("您要输入多少个学生的成绩");
            n=reader.nextInt();
            if(n<=0)
              System.out.println("个数错误!");
                 else
                         {
                          score=new double[n];
                   for(int i=0;i<n;i++){
                      System.out.print("请输入第"+(i+1)+"个童鞋的成绩:");
                      score[i]=reader.nextDouble();
                }
                Info info = new Info();
                  info.showInfo(n,score);  
              }               
            
    }
}
    class Info{
        public void showInfo(int n,double score[]){
            Scanner reader=new Scanner(System.in);
            System.out.println("您想查找第几个童鞋的成绩?");
              int index=reader.nextInt();
                if(index>0&&index<=n)
                System.out.println("第"+index+"个童鞋的成绩是"+score[index-1]);
                else
                 System.out.println("对不起，您输入的数字有误!");
      }


    }

哦~~忘定义了

我用你提供的代码试了一下，貌似不能正确执行啊