我现在有点困惑。我使用此函数将2D String数组重写为2D double数组。但是它正在抛出nullpointer异常。 d2中的数据格式为：
String [i] [0/1]，其中0和1是格式为“ 0.3343434”的数字。
public void StringToDouble () {
unsorted = new double[d2.length][2];
for(int i = 0; i < d2.length; i++)
{
unsorted[i][0] = Double.parseDouble(d2[i][0]);
unsorted[i][1] = Double.parseDouble(d2[i][1]);
}
}
当我打印unsorted [0] [0]和[1] [1]时出现错误。
这是完整的代码。
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Scanner;
public class LoadAndSort {
String raw;
double [][] data;
String [] datastring;
// 2D CONVERT
String [] d1;
String [][] d2;
double[][] unsorted;
double [][] sorted;
String path = "src/data.dat";
public LoadAndSort () throws IOException {
// # Reads file from disk and stores to variable.
datas = readFile(path);
// # Splits the content, and sorts it into a huge string with relevant variables.
// # Splits on newline to order the lines.
d1 = datas.split("\\r?\\n");
// # Splits on comma to convert to 2D Array.
Convert2D();
// # Mirrors the 2D array because Mikal is gay.
//MirrorArray();
//StringToDouble();
System.out.println(unsorted[0][0]);
System.out.println(unsorted[0][1]);
}
private static String readFile(String path) throws IOException {
FileInputStream stream = new FileInputStream(new File(path));
try {
FileChannel fc = stream.getChannel();
MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
/* Instead of using default, pass in a decoder. */
return Charset.defaultCharset().decode(bb).toString();
}
finally {
stream.close();
}
}
public void Convert2D () {
d2 = new String[d1.length][];
int r = 0;
for (String row : d1) {
d2[r++] = row.split(",");
}
}
public void StringToDouble () {
unsorted = new double[d2.length][2];
for(int i = 0; i < d2.length; i++)
{
unsorted[i][0] = Double.parseDouble(d2[i][0]);
System.out.println(d2[i][0]);
unsorted[i][1] = Double.parseDouble(d2[i][1]);
}
}
}
和来自控制台的错误：
0.00965821033009
Exception in thread "main" java.lang.NullPointerException
at LoadAndSort.<init>(LoadAndSort.java:48)
at Runner.main(Runner.java:13)
最佳答案
您可以在unsorted（使用StringToDouble）中初始化unsorted = new double[d2.length][2];，但是构造函数中的函数调用当前已被注释掉，因此unsorted将永远不会初始化。
因此它将是null，并且将在此处抛出NullPointerException：
System.out.println(unsorted[0][0]);
不确定这是否是唯一的问题，但首先要解决。