虽然声明了数组的类型为Student，且数组的长度为3，但是并没有创建Student对象，这就是造成空指针异常的原因。解决方式如下：

import java.util.Scanner;

public class J_ava8 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        Student[] s = new Student[3];
        for (Student S : s) {
            S = new Student();
            System.out.println("Please input the student's name:");
            S.setName(in.next());
            System.out.println("Please input the number:");
            S.setNumber(in.next());
            System.out.println("Please input the ChieseScore:");
            S.setChineseScore(in.nextInt());
            System.out.println("Please input the MathScore:");
            S.setMathScore(in.nextInt());
            System.out.println("Please input the EnglisnScore");
            S.setEnglishScore(in.nextInt());
            S.ShowAllInfo();
        }
        in.close();
    }
}

class Student {
    private String Name;
    private String Number;
    private int ChineseScore;
    private int MathScore;
    private int EnglishScore;

    public void setName(String name) {
        this.Name = name;
    }

    public void setNumber(String number) {
        this.Number = number;
    }

    public void setChineseScore(int chineseScore) {
        this.ChineseScore = chineseScore;
    }

    public void setMathScore(int mathScore) {
        this.MathScore = mathScore;
    }

    public void setEnglishScore(int englishScore) {
        this.EnglishScore = englishScore;
    }

    public void ShowAllInfo() {
        System.out.println("name:" + Name + "number" + Number +

                    "chineseScore" + ChineseScore + "mathScore" + MathScore +

                    "englishScore" + EnglishScore);
    }
}