《Java编程思想》学习笔记14——I/O高级

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import java.nio.*;
import java.nio.channels.*;
import java.io.*;
pulbic class MemoryMappedFile{
//十六进制，128MB大小
static int length = 0x8FFFFFF;
public static void main(String[] args)throws Exception{
//通过文件通道将文件映射为内存中的自己缓冲区
MappedByteBuffer out = new RandomAccessFile(“test.dat”, “rw”).getChannel()
.map(FileChannel.MapMode.READ_WRITE, 0, length);
for(int i = 0; i < length; i++){
out.put((byte)’x’);
}
System.out.println(“Finished writing”);
for(int I = length/2; i < length/2 + 6; i++){
System.out.println((char)out.get(i));
}
}
}

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import java.nio.channels.*;
import java.util.concurrent.*;
import java.io.*;
public class FileLocking{
public static void main(String[] args)throws Exception{
FileOutputStream fos = new FileOutputStream(“file.txt”);
//试图对文件通道的文件锁定
FileLock fl = fos.getChannel().tryLock();
//文件锁定成功
if(fl != null){
System.out.println(“Locked File”);
TimeUnit.MILLISECONDS.sleep(100);
//释放文件锁
fl.release();
System.out.println(“Released Lock”);
}
foc.close();
}
}

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import java.util.zip.*;
import java.io.*;
public class GZIPCompress{
public static void main(String[] args)throws IOException{
BufferedReader in = new BufferedReader(new FileReader(“test.dat”));
BufferedOutputStream out = new BufferedOutputStream(new GZIPOutputStream(
new FileOutputStream(“test.gz”)));
int c;
//写GZIP格式压缩文件
while((c = in.read()) != -1){
out.write(c);
}
in.close();
out.close();
BufferedReader in2 = new BufferedReader(new InputStreamReader(
new GZIPInputStream(new FileInputStream(“test.gz”))));
String s;
//读取GZIP格式压缩文件
while((s = in2.readLine()) != null){
System.out.println(s);
}
in2.close();
}
}

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import java.util.zip.*;
import java.io.*;
import java.util.*;
public class ZipCompress{
public static void main(String[] args)throws Exception{
FileOutputStream f = new FileOutputStream(“test.zip”);
//使用Adler32算法为文件输入流产生输出校验和文件
CheckedOutputStream csum = new CheckedOutputStream(f, new Adler32());
ZipOutputStream zos = new ZipOutputStream(csum);
BufferedOutputStream out = new BufferedOutputStream(zos);
//设置zip文件注释
zos.setComment(“A test of java zipping”);
//向zip压缩文件写入多个文件
for(String arg : args){
System.out.println(“Writing file:” + arg);
BufferedReader in = new BufferedReader(new FileReader(arg));
//写入一个zip文件条目，并将流定位到条目数据的开始处
zos.putNextEntry(new ZipEntry(arg));
int c;
//写入zip文件内容
while((c = in.read()) != -1){
out.write(c);
}
in.close();
out.flush();
}
out.close();
//文件关闭后获取校验和
System.out.println(“Checksum:” + csum.getChecksum().getValue());
FileInputStream fi = new FileInputStream(“test.zip”);
//使用Adler32算法为输入文件流产生输入校验和文件流
CheckedInputStream csumi = new CheckedInputStream(fi, new Adler32());
ZipInputStream in2 = new ZipInputStream(csumi);
BufferedInputStream bis = new BufferedInputStream(in2);
ZipEntry ze;
//读取zip文件条目
While((ze = in2.getNextEntry()) != null){
System.out.println(“Reading file:” + ze);
int x;
//读取zip文件条目内容
while((x = bis.read()) != -1){
System.out.println(x);
}
}
if(args.length == 1){
System.out.println(“Checksum:” + csumi.getChecksum().getValue());
}
bis.close();
//另一种读取zip文件的方法
ZipFile zf = new ZipFile(“test.zip”);
//获取zip文件的条目
Enumeration e = zf.entries();
while(e.hasMoreElements()){
ZipEntry ze2 = (ZipEntry)e.nextElement();
System.out.println(“Reading File:” + ze2);
}
}
}