Java如何使用DataInputStream和DataOutputStream？
java.io.DataOutputStream以及java.io.DataInputStream文件使我们能够将原始数据类型写入和读取到文件等媒体。这两个类都有相应的方法来写入和读回原始数据类型。
使用这个类使其更易于阅读int，float，double数据等，而无需解释，如果数据应该是一个int或一个float数据。让我们在下面看我们的代码。
package org.nhooo.example.io;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class PrimitiveStreamExample {
public static void main(String[] args) {
// 准备一些要写入文件的数据。
int cityIdA = 1;
String cityNameA = "Green Lake City";
int cityPopulationA = 500000;
float cityTempA = 15.50f;
int cityIdB = 2;
String cityNameB = "Salt Lake City";
int cityPopulationB = 250000;
float cityTempB = 10.45f;
/*
Create an instance of FileOutputStream with cities.dat as the file
name to be created. Then we pass the input stream object in the
DataOutputStream constructor.
*/
try (FileOutputStream fos = new FileOutputStream("cities.dat");
DataOutputStream dos = new DataOutputStream(fos)) {
/*
Below we write some data to the cities.dat. DataOutputStream
class have various method that allow us to write primitive type
data and string. There are method called writeInt(),
writeFloat(), writeUTF(), etc.
*/
dos.writeInt(cityIdA);
dos.writeUTF(cityNameA);
dos.writeInt(cityPopulationA);
dos.writeFloat(cityTempA);
dos.writeInt(cityIdB);
dos.writeUTF(cityNameB);
dos.writeInt(cityPopulationB);
dos.writeFloat(cityTempB);
} catch (IOException e) {
e.printStackTrace();
}
/*
Now we have a cities.dat file with some data in it. Next you'll see
how easily we can read back this data and display it. Just like the
DataOutputStream the DataInputStream class have the corresponding
read methods to read data from the file. Some of the method names
are readInt(), readFloat(), readUTF(), etc.
*/
try (FileInputStream fis = new FileInputStream("cities.dat");
DataInputStream dis = new DataInputStream(fis)) {
// 读取第一个数据
int cityId1 = dis.readInt();
String cityName1 = dis.readUTF();
int cityPopulation1 = dis.readInt();
float cityTemperature1 = dis.readFloat();
printOut(cityId1, cityName1, cityPopulation1, cityTemperature1);
// 读取第二个数据
int cityId2 = dis.readInt();
String cityName2 = dis.readUTF();
int cityPopulation2 = dis.readInt();
float cityTemperature2 = dis.readFloat();
printOut(cityId2, cityName2, cityPopulation2, cityTemperature2);
} catch (IOException e) {
e.printStackTrace();
}
}
private static void printOut(int cityId1, String cityName1, int cityPopulation1, float cityTemperature1) {
System.out.println("Id: " + cityId1);
System.out.println("Name: " + cityName1);
System.out.println("Population: " + cityPopulation1);
System.out.println("Temperature: " + cityTemperature1);
}
}我们程序的生成结果是：
Id: 1 Name: Green Lake City Population: 500000 Temperature: 15.5 Id: 2 Name: Salt Lake City Population: 250000 Temperature: 10.45