java - 在java中分配不同的值后，每一行在二维数组中获得相同的值

Question

'''

FileChannel channel = new FileInputStream("test.txt").getChannel();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0,50000);
    byte[] data = new byte[102];
    byte[][] bufferArray = new byte[(buffer.capacity() / 102)][100];
    int i = 0;
    while (buffer.hasRemaining()) {
        int remaining = data.length;
        if (buffer.remaining() < remaining)
            remaining = buffer.remaining();
        buffer.get(data, 0, remaining);

        bufferArray[i++] = data;
        System.out.println("Value before " + new String(bufferArray[43777]));
        System.out.println("Value before 0 " + new String(bufferArray[0]));
        System.out.println("Value before 100 " + new String(bufferArray[100]));
    }
    System.out.println("Value after 0 " + new String(bufferArray[0]));
    System.out.println("Value after 100 " + new String(bufferArray[100]));
    System.out.println("Value after 43777 " + new String(bufferArray[43777]));

'''* 前面的值不同，但后面的值都相同*buffer 是从 txt 文件读取的 MappedByteBuffer

Answer 1

将数据数组初始化移至循环内。通过将其保留在代码之外，代码会重复覆盖相同的内存

FileChannel channel = new FileInputStream("test.txt").getChannel();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0,50000);
    byte[] data;
    byte[][] bufferArray = new byte[(buffer.capacity() / 102)][100];
    int i = 0;
    while (buffer.hasRemaining()) {
        data = new byte[102];
        int remaining = data.length;
        if (buffer.remaining() < remaining)
            remaining = buffer.remaining();


        buffer.get(data, 0, remaining);
        bufferArray[i++] = data;
        System.out.println("Value before " + new String(bufferArray[43777]));
        System.out.println("Value before 0 " + new String(bufferArray[0]));
        System.out.println("Value before 100 " + new String(bufferArray[100]));
    }
    System.out.println("Value after 0 " + new String(bufferArray[0]));
    System.out.println("Value after 100 " + new String(bufferArray[100]));
    System.out.println("Value after 43777 " + new String(bufferArray[43777]));