为什么我在“plain1.findPosition（iMsg）”上收到 NullPointerException？

问：

头等舱给了我错误。我将用字母 A-Z 创建一个数组，然后让用户输入它所采用的键，并将每个字符在键数组中的位置与用户输入的字符串的位置进行比较

import java.util.*;
    public class Encrypt{
        private Square plain1;
        private Square plain2;
        private Square Encrypt1;
        private Square Encrypt2;

    public Encryption(String key1, String key2) {
        Square plain1 = new Square();
        Square plain2 = new Square();
        Square Encrypt1= new Square(key1);
        Square Encrypt2= new Square(key2);
    } 


    public String encrypt(String msg) {
        String EmpS = "";
        String STR = "";

        for(int i = 0; i < message.length(); i+=2){
            char iMsg = message.charAt(i);
            char iMsg2 = message.charAt(i+1);
            int[] posRay = plain1.findPosition(iMsg);
            int[] posRay2 = plain2.findPosition(iMsg2);
            String answer = "" + Encrypt1.getChar(posRay[0], posRay2[1]);
            String Combined = "" + answer;
            String answer2 = "" + Encrypt2.getChar(posRay2[0], posRay[1]);
            String Combined2 = "" + answer2;

            String BothCom = Combined + Combined2;
            STR = STR.concat(BothCom);

        return STR;
        }
        return STR;
    } 

负责数组的第 2 类

public class Square {
    private char[][] matrix;
public Square() {
        arr= new char[5][5];
        int ascii= 65;
        for (int i = 0; i < 5; i++){
            for(int j = 0; j < 5; j++){
                arr[i][j] = (char) ascii;
                ascii++;
                }
            }
        }
}
public int[] findPosition(char Chart) {
        int[] position= new int[2];
        position[0] = -1;
        popositions[1] = -1;
        for (int i = 0; i < 5; i++){
            for (int j = 0; i < 5; j++){
                if(matrix[i][j] == Chart){
                posistion[0] = i;
                position[1] = j;
                return position;
                }
            }
        }

我把它当作一个错误（其他一切都有效），有什么问题？

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "Square.getPos(char)" because "this.plain1" is null
        at findPosition.encrypt(Encrypt.java:45)
        at IO.printResults(IO.java:101)
        at Test.main(Proj8.java:26)