jdk7以后,通过try-with-resources技术,可以在try中实例化资源,让它在结束后自动关闭.
package stream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class TestStream {
public static void main(String[] args) {
File f = new File("d:/lol.txt");
//把流定义在try()里,try,catch或者finally结束的时候，会自动关闭
try (FileInputStream fis = new FileInputStream(f)) {
byte[] all = new byte[(int) f.length()];
fis.read(all);
for (byte b : all) {
System.out.println(b);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
jdk9中,可以直接在try中使用常量资源,而不需要重新定义了.
// New and improved try-with-resources statement in JDK 9
try (resource1;
resource2) {
// Use of resource1 and resource 2.
}
流流
InputStream输入流/OutputStream输出流.字节输入输出
FileInputStream fis = new FileInputStream(new File("C:/"));
Reader字符输入流Writer字符输出流(默认按操作系统编码GBK)
FileReader fr = new FileReader(f);
自定义编码字符流InputStreamReader
InputStreamReader isr = new InputStreamReader(new FileInputStream(f),Charset.forName("UTF-8"))
字符缓存流BufferedReader PrintWriter flush
try (
FileReader fr = new FileReader(f);
BufferedReader br = new BufferedReader(fr);
)
{
while (true) {
// 一次读一行
String line = br.readLine();
if (null == line)
break;
System.out.println(line);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try (
// 创建文件字符流
FileWriter fw = new FileWriter(f);
// 缓存流必须建立在一个存在的流的基础上
PrintWriter pw = new PrintWriter(fw);
) {
pw.println("garen kill teemo");
pw.println("teemo revive after 1 minutes");
pw.println("teemo try to garen, but killed again");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//向文件lol2.txt中写入三行语句
File f =new File("d:/lol2.txt");
//创建文件字符流
//缓存流必须建立在一个存在的流的基础上
try(FileWriter fr = new FileWriter(f);PrintWriter pw = new PrintWriter(fr);) {
pw.println("garen kill teemo");
//强制把缓存中的数据写入硬盘，无论缓存是否已满
pw.flush();
pw.println("teemo revive after 1 minutes");
pw.flush();
pw.println("teemo try to garen, but killed again");
pw.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
数据流DataInputStream数据输入流 DataOutputStream数据输出流
数据输入流只能识别数据输出流写入的数据.
优点在于可以直接读取不同类型的数据.
package stream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class TestStream {
public static void main(String[] args) {
write();
read();
}
private static void read() {
File f =new File("d:/lol.txt");
try (
FileInputStream fis = new FileInputStream(f);
DataInputStream dis =new DataInputStream(fis);
){
boolean b= dis.readBoolean();
int i = dis.readInt();
String str = dis.readUTF();
System.out.println("读取到布尔值:"+b);
System.out.println("读取到整数:"+i);
System.out.println("读取到字符串:"+str);
} catch (IOException e) {
e.printStackTrace();
}
}
private static void write() {
File f =new File("d:/lol.txt");
try (
FileOutputStream fos = new FileOutputStream(f);
DataOutputStream dos =new DataOutputStream(fos);
){
dos.writeBoolean(true);
dos.writeInt(300);
dos.writeUTF("123 this is gareen");
} catch (IOException e) {
e.printStackTrace();
}
}
}
对象流ObjectInputStream/ObjectOutputStream
实现了Serializable接口的类的对象可以进行序列化.
package stream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import charactor.Hero;
public class TestStream {
public static void main(String[] args) {
//创建一个Hero garen
//要把Hero对象直接保存在文件上，务必让Hero类实现Serializable接口
Hero h = new Hero();
h.name = "garen";
h.hp = 616;
//准备一个文件用于保存该对象
File f =new File("d:/garen.lol");
try(
//创建对象输出流
FileOutputStream fos = new FileOutputStream(f);
ObjectOutputStream oos =new ObjectOutputStream(fos);
//创建对象输入流
FileInputStream fis = new FileInputStream(f);
ObjectInputStream ois =new ObjectInputStream(fis);
) {
oos.writeObject(h);
Hero h2 = (Hero) ois.readObject();
System.out.println(h2.name);
System.out.println(h2.hp);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
控制台输入流System.in
用Scanner更加方便的使用控制台输入吧.
Scanner s = new Scanner(System.in);