将 .dat 文件读入 Java 中的数组
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Reading a .dat file into an array in Java
提问by Ben
The code that I'm writing has two classes: writeInts and readInts. I wrote writeInts to randomly generate 100 numbers between 0 and 1000 and output them to a data.dat file.
我正在编写的代码有两个类：writeInts 和 readInts。我写了 writeInts 来随机生成 0 到 1000 之间的 100 个数字并将它们输出到 data.dat 文件。
readInts is supposed to open a DataInputStream object and read in the "raw" data from the data.dat file and store the 100 integers in an array. My problem is that I can't seem to read the data correctly. Any help with this would be greatly appreciated. Thanks!
readInts 应该打开一个 DataInputStream 对象并从 data.dat 文件中读取“原始”数据并将 100 个整数存储在一个数组中。我的问题是我似乎无法正确读取数据。对此的任何帮助将不胜感激。谢谢！
writeInts:
写整数：
import java.io.*;
public class WriteInts {
public static void main(String[] args) throws IOException {
DataOutputStream output = new DataOutputStream(new FileOutputStream("data.dat"));
int num = 0 + (int)(Math.random());
int[] counts = new int[100];
for(int i=0; i<100; i++) {
output.writeInt(num);
counts[i] += num;
System.out.println(num);
}
output.close();
}
}
readInts:
读入：
import java.io.*;
import java.util.*;
public class ReadInts {
public static void main(String[] args) throws IOException {
// call the file to read
Scanner scanner = new Scanner(new File("data.dat"));
int[] data = new int[100];
int i = 0;
while (scanner.hasNextInt()) {
data[i++] = scanner.nextInt();
System.out.println(data[i]);
scanner.close();
}
}
}
采纳答案by Denis Kulagin
If you want to write binary data, use DataInputStream/DataOutputStream. Scanneris for text dataand you can't mix it.
如果要写入二进制数据，请使用DataInputStream/DataOutputStream。扫描仪用于文本数据，您不能混合使用。
WriteInts:
写入整数：
import java.io.*;
public class WriteInts {
public static void main(String[] args) throws IOException {
DataOutputStream output = new DataOutputStream(new FileOutputStream(
"data.dat"));
for (int i = 0; i < 100; i++) {
output.writeInt(i);
System.out.println(i);
}
output.close();
}
}
ReadInts:
读取数据：
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class ReadInts {
public static void main(String[] args) throws IOException {
DataInputStream input = new DataInputStream(new FileInputStream(
"data.dat"));
while (input.available() > 0) {
int x = input.readInt();
System.out.println(x);
}
input.close();
}
}
回答by duffymo
I'd recommend that you abandon DataInputStreamand DataOutputStream.
我建议你放弃DataInputStream和DataOutputStream。
Write the ints one to a line using FileWriterand read them using a BufferedReader, one per line. This is an easy problem.
将整数写入一行FileWriter并使用 a 读取它们BufferedReader，每行一个。这是一个简单的问题。
回答by Denis Kulagin
More. If you want to generate a random number in range from 0 to 1000 (both inclusive), you use this statement:
更多的。如果要生成 0 到 1000（包括两者）范围内的随机数，请使用以下语句：
int rndNum = (int) (Math.random() * 1001);
It works that way: Math.random()generates a double in range from 0 to 1 (exclusive), which you then should map to integer range and floor. If you want you maximal value to be 1000, you multiply it by 1001 - 1001 itself is excluded.
它是这样工作的：Math.random()生成一个范围从 0 到 1（不包括）的双精度值，然后您应该将其映射到整数范围和下限。如果您希望最大值为 1000，则将其乘以 1001 - 1001 本身被排除在外。
Yep, like that:
是的，就像这样：
import java.io.*;
public class WriteRandomInts {
public static void main(String[] args) throws IOException {
DataOutputStream output = new DataOutputStream(new FileOutputStream(
"data.dat"));
for (int i = 0; i < 100; i++) {
int rndNum = (int) (Math.random() * 1001);
output.writeInt(rndNum);
System.out.println(rndNum);
}
output.close();
}
}
