支持ZIP格式的Java庫更加全面。利用該庫可以方便地保存多個文件,他甚至有一個獨立的類,是的讀取ZIP文件更加方便。這個類庫使用的是標準ZIP格式,所以能與當前那些可通過因特網下載的壓縮工具很好的協作。使用zip保存,需要使用Checksum類來計算和校驗文件的校驗和的方法。一共有兩種Checksum類型:Adler32(它快一些)和CRC32(慢一些,但更準確)。
package java186;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.util.Enumeration;
import java.util.zip.Adler32;
import java.util.zip.CheckedInputStream;
import java.util.zip.CheckedOutputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;
public class ZipCompress {
public static void main(String[] args) throws Exception{
args = new String[3];
args[0] = "d:/file/data.txt";
args[1] = "d:/file/DirList.java";
args[2] = "test.txt";
FileOutputStream f = new FileOutputStream("d:/file/test.zip");
CheckedOutputStream csum = new CheckedOutputStream(f, new Adler32());
ZipOutputStream zos = new ZipOutputStream(csum);
BufferedOutputStream out = new BufferedOutputStream(zos);
zos.setComment("A test of Java Zipping");
for(String arg : args){
System.out.println("writing file: "+arg);
BufferedReader in = new BufferedReader(new FileReader(arg));
zos.putNextEntry(new ZipEntry(arg));
int c;
while((c=in.read())!=-1){
out.write(c);
}
in.close();
out.flush();
}
out.close();
System.out.println("CheckSum: "+csum.getChecksum().getValue());
System.out.println("Reading file");
FileInputStream fi = new FileInputStream("d:/file/test.zip");
CheckedInputStream csumi = new CheckedInputStream(fi, new Adler32());
ZipInputStream in2 = new ZipInputStream(csumi);
BufferedInputStream bis = new BufferedInputStream(in2);
ZipEntry ze;
while((ze=in2.getNextEntry())!=null){
System.out.println("Reading file "+ze);
int x;
while((x=bis.read())!=-1){
System.out.write(x);
}
}
if(args.length==1)System.out.println("Checksum: "+csumi.getChecksum().getValue());
bis.close();
ZipFile zf = new ZipFile("d:/file/test.zip");
Enumeration e = zf.entries();
while(e.hasMoreElements()){
ZipEntry ze2 = (ZipEntry) e.nextElement();
System.out.println("File: "+ze2);
}
}
}
爲了能夠解壓縮文件,ZipInputStream提供了一個getNextEntry()方法返回下一個ZipEntry(如果存在的話)。解壓縮文件有一個更簡便的方法-------利用ZipFile對象讀取文件。該對象有個entries()方法用來向ZipEntries返回一個Enumeration(枚舉)。