Question

我在访问此循环之外的2D数组（myArray）时遇到了一些问题。我想使用其他方法访问它，但我甚至无法在此方法中访问它。它在循环时打印正确，但是

的测试打印

System.out.println(myArray[10][2]);

始终为null。所以它就像阵列实际上没有填充或其他东西。谁知道我在这里做错了什么？

package titanic;

import java.io.*;
import java.util.*;

public class Titanic {


public static final int ROW = 1309;
public static final int COLUMN = 6;
public static String [][] myArray = new String[ROW][COLUMN];


public static String[][] arraySetup(){

    int recordCounter = 0;
    String[][] myArray = new String[ROW][COLUMN];
    String[] name = new String [ROW];
    try {
        BufferedReader br = new BufferedReader(new FileReader("C:/Users/Tom/Desktop/Titanic.txt"));
        String line;
        for (int i = 0; i < 1309; i++){
        while((line = br.readLine()) != null){

            String tmp[] = line.split("\t");
                myArray[i][0] = tmp[0];
                myArray[i][1] = tmp[1];
                myArray[i][2] = tmp[2];
                myArray[i][3] = tmp[3];
                myArray[i][4] = tmp[4];
                myArray[i][5] = tmp[5];
                System.out.println("myArray[i][5] = " + myArray[i][5]);
                recordCounter++;

            }
        }

    } catch (IOException e) {
        e.printStackTrace();
    }
    System.out.println(myArray[10][2]);

    System.out.println(recordCounter + " records.");
    return myArray;
}

Answer 1

正如您在while循环中循环用于索引输出数组for的循环一样，循环总是写入while到myArray[0][0]

myArray[0][5]

因此，您的检查始终返回null。

    for (int i = 0; i < 1309; i++){   // i is 0
    while((line = br.readLine()) != null){   // you go through all the lines while i is 0

        String tmp[] = line.split("\t");
            myArray[i][0] = tmp[0];
            myArray[i][1] = tmp[1];
            myArray[i][2] = tmp[2];
            myArray[i][3] = tmp[3];
            myArray[i][4] = tmp[4];
            myArray[i][5] = tmp[5];
            System.out.println("myArray[i][5] = " + myArray[i][5]);
            recordCounter++;

        }
    }

Answer 2

不要一起使用for和while循环。在第一个for循环期间，while读取所有文件内容，所有其他数组位置保持为空。试试这个：

int i=0;
while ((line = br.readLine()) != null){
    String tmp[] = line.split("\t");
     myArray[i][0] = tmp[0];
     myArray[i][1] = tmp[1];
     ...       
     myArray[i][5] = tmp[5];

     i++;
     System.out.println("myArray[i][5] = " + myArray[i][5]);
     recordCounter++;
}

Answer 3

我认为代码中的问题就在那里

for (int i = 0; i < 1309; i++){ // you loop 1308 time
        while((line = br.readLine()) != null){ /* in each loop, you loop 
 until you have read all the file so you read 1308 time the file. But when 
you reach the end of file on the first iterration, it wont read the file on the 1307
 other iterration  and all data will be store in myArray[0][0-5]*/

            String tmp[] = line.split("\t");
                myArray[i][0] = tmp[0];
                myArray[i][1] = tmp[1];
                myArray[i][2] = tmp[2];
                myArray[i][3] = tmp[3];
                myArray[i][4] = tmp[4];
                myArray[i][5] = tmp[5];
                System.out.println("myArray[i][5] = " + myArray[i][5]);
                recordCounter++;

            }
        }

为什么我不能在循环外访问我的2D数组？

3 个答案: