10.8 压缩
10.8 压缩
此时
CheckedInputStream GetCheckSum()为任何InputStream产生校验和(不仅是解压)
CheckedOutputStream GetCheckSum()为任何OutputStream产生校验和(不仅是解压)
DeflaterOutputStream 用于压缩类的基础类
ZipOutputStream 一个DeflaterOutputStream,将数据压缩成Zip文件格式
GZIPOutputStream 一个DeflaterOutputStream,将数据压缩成GZIP文件格式
InflaterInputStream 用于解压类的基础类
ZipInputStream 一个DeflaterInputStream,解压用Zip文件格式保存的数据
GZIPInputStream 一个DeflaterInputStream,解压用GZIP文件格式保存的数据
尽管存在许多种压缩算法,但是
//: GZIPcompress.java
// Uses Java 1.1 GZIP compression to compress
// a file whose name is passed on the command
// line.
import java.io.*;
import java.util.zip.*;
public class GZIPcompress {
public static void main(String[] args) {
try {
BufferedReader in =
new BufferedReader(
new FileReader(args[0]));
BufferedOutputStream out =
new BufferedOutputStream(
new GZIPOutputStream(
new FileOutputStream("test.gz")));
System.out.println("Writing file");
int c;
while((c = in.read()) != -1)
out.write(c);
in.close();
out.close();
System.out.println("Reading file");
BufferedReader in2 =
new BufferedReader(
new InputStreamReader(
new GZIPInputStream(
new FileInputStream("test.gz"))));
String s;
while((s = in2.readLine()) != null)
System.out.println(s);
} catch(Exception e) {
e.printStackTrace();
}
}
} ///:~
压缩类的用法非常直观——只需将输出流封装到一个
提供了
//: ZipCompress.java
// Uses Java 1.1 Zip compression to compress
// any number of files whose names are passed
// on the command line.
import java.io.*;
import java.util.*;
import java.util.zip.*;
public class ZipCompress {
public static void main(String[] args) {
try {
FileOutputStream f =
new FileOutputStream("test.zip");
CheckedOutputStream csum =
new CheckedOutputStream(
f, new Adler32());
ZipOutputStream out =
new ZipOutputStream(
new BufferedOutputStream(csum));
out.setComment("A test of Java Zipping");
// Can't read the above comment, though
for(int i = 0; i < args.length; i++) {
System.out.println(
"Writing file " + args[i]);
BufferedReader in =
new BufferedReader(
new FileReader(args[i]));
out.putNextEntry(new ZipEntry(args[i]));
int c;
while((c = in.read()) != -1)
out.write(c);
in.close();
}
out.close();
// Checksum valid only after the file
// has been closed!
System.out.println("Checksum: " +
csum.getChecksum().getValue());
// Now extract the files:
System.out.println("Reading file");
FileInputStream fi =
new FileInputStream("test.zip");
CheckedInputStream csumi =
new CheckedInputStream(
fi, new Adler32());
ZipInputStream in2 =
new ZipInputStream(
new BufferedInputStream(csumi));
ZipEntry ze;
System.out.println("Checksum: " +
csumi.getChecksum().getValue());
while((ze = in2.getNextEntry()) != null) {
System.out.println("Reading file " + ze);
int x;
while((x = in2.read()) != -1)
System.out.write(x);
}
in2.close();
// Alternative way to open and read
// zip files:
ZipFile zf = new ZipFile("test.zip");
Enumeration e = zf.entries();
while(e.hasMoreElements()) {
ZipEntry ze2 = (ZipEntry)e.nextElement();
System.out.println("File: " + ze2);
// ... and extract the data as before
}
} catch(Exception e) {
e.printStackTrace();
}
}
} ///:~
对于要加入压缩档的每一个文件,都必须调用
为解压文件,
为读取校验和,必须多少拥有对关联的
当然,使用
涉及因特网应用时,
一个
jar [选项] 说明 [详情单] 输入文件
其中
c 创建新的或空的压缩档
t 列出目录表
x 解压所有文件
x file 解压指定文件
f 指出“我准备向你提供文件名”。若省略此参数,jar会假定它的输入来自标准输入;或者在它创建文件时,输出会进入标准输出内
m 指出第一个参数将是用户自建的详情表文件的名字
v 产生详细输出,对jar做的工作进行巨细无遗的描述
O 只保存文件;不压缩文件(用于创建一个JAR文件,以便我们将其置入自己的类路径中)
M 不自动生成详情表文件
在准备进入
下面是调用
jar cf myJarFile.jar *.class
用于创建一个名为
jar cmf myJarFile.jar myManifestFile.mf *.class
与前例类似,但添加了一个名为
jar tf myJarFile.jar
生成
jar tvf myJarFile.jar
添加“verbose”(详尽)标志,提供与
jar cvf myApp.jar audio classes image
假定
如果用
CLASSPATH="lib1.jar;lib2.jar;"
正如大家在第