java数组打印为空

Question

你好，我正在制作一个警报程序，我在从 db.txt 文件中收集数据时遇到了问题，我试图这样做System.out.println(array[]); 但它没有做任何事情我想知道是否有可能创建一个 int 让它称之为数字并使用它来选择一个数组来打印，就像这样System.out.println(array[number]); 无论如何这就是我想要做的，它仍然返回空值。 这是我的 Java 代码：

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import javax.swing.*;

public class alarm {
public static JFrame window;
public JPanel p;
public RandomAccessFile rw;
    alarm() throws IOException {
        window = new JFrame();
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setResizable(false);
        window.setSize(600, 600);
        p = new JPanel();
        p.setLayout(null);
        try {
            rw = new RandomAccessFile("db.txt", "rw");
            int loop = 0;
            int insertNumber = 0;
            int[] numberArray = new int[1000000];
            String[] name = new String[1000000];
            String[] desc = new String[1000000];
            String[] date = new String[1000000];
            String row = null;
            while(loop == 0) {
                 row = rw.readLine();
                 if(row == "/") {
                    insertNumber = insertNumber + 1;
                    insertNumber = numberArray[insertNumber];
                    name[insertNumber] = rw.readLine();
                    desc[insertNumber] = rw.readLine();
                    date[insertNumber] = rw.readLine();
                }
               if(row == null) {
                    insertNumber = 0;
                    loop = 1;   
                }
        }
        System.out.println("Arrays loaded");
            while(loop == 1) {
            insertNumber = insertNumber + 1;
            if(name[insertNumber] == null) {
                loop = 2;
            }
            System.out.println(name[insertNumber]);
        } 
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}
public static void main(String[] args) throws IOException {
    new alarm();
    window.setVisible(true);
}

}

Answer 1

您将索引insertNumber增加到下一个值，该值在数组中为 null ，然后打印它。

while(loop == 1) {
     insertNumber = insertNumber + 1; // insertNumber is incr. before index 0 is printed
     if(name[insertNumber] == null) {  // Always true if size < 2 elements
        loop = 2;
     }
     System.out.println(name[insertNumber]); //prints null is size < 2
}     

试试吧：

for(String element : name) {
     System.out.println(element + " ");
}

此外，这一行是不正确的：

insertNumber = numberArray[insertNumber];