int read(byte[] b, int off, int len)

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2023-12-01

描述 (Description)

java.util.zip.ZipInputStream.read(byte[] buf, int off, int len)方法从当前ZIP条目读入字节数组。 如果len不为零,则该方法将阻塞,直到某些输入可用为止; 否则,不读取任何字节,返回0。

声明 (Declaration)

以下是java.util.zip.ZipInputStream.read(byte[] buf, int off, int len)方法的声明。

public int read(byte[] buf, int off, int len)
   throws IOException

参数 (Parameters)

  • buf - 读取数据的缓冲区。

  • off - 目标数组中的起始偏移量b。

  • len - 读取的最大字节数。

返回值 (Returns)

读取的实际字节数,如果到达流的末尾,则返回-1。

异常 (Exceptions)

  • NullPointerException - 如果buf为null。

  • IndexOutOfBoundsException - 如果off为负数,则len为负数,或者len为buf.length-off。

  • ZipException - 如果发生ZIP文件错误。

  • IOException - 如果发生I/O错误。

先决条件

D:》 test 》目录中创建一个文件Hello.txt,其中包含以下内容。

This is an example.

例子 (Example)

以下示例显示了java.util.zip.ZipInputStream.read(byte [] buf,int off,int len)方法的用法。

package cn.xnip;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Date;
import java.util.zip.Adler32;
import java.util.zip.CheckedOutputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;
public class ZipInputStreamDemo {
   private static String SOURCE_FILE = "D:\\test\\Hello.txt";
   private static String TARGET_FILE = "D:\\test\\Hello.zip";
   public static void main(String[] args) {
      try {
         createZipFile();
         readZipFile();
      } catch(IOException ioe) {
         System.out.println("IOException : " + ioe);
      }
   }
   private static void createZipFile() throws IOException{
      FileOutputStream fout = new FileOutputStream(TARGET_FILE);
      CheckedOutputStream checksum = new CheckedOutputStream(fout, new Adler32());
      ZipOutputStream zout = new ZipOutputStream(checksum);
      FileInputStream fin = new FileInputStream(SOURCE_FILE);
      ZipEntry zipEntry = new ZipEntry(SOURCE_FILE);
      zout.putNextEntry(zipEntry);
      int length;
      byte[] buffer = new byte[1024];
      while((length = fin.read(buffer)) > 0) {
         zout.write(buffer, 0, length);
      }
      zout.closeEntry();
      fin.close();
      zout.close();
   }
   private static void readZipFile() throws IOException{
      ZipInputStream zin = new ZipInputStream(new FileInputStream(TARGET_FILE)); 
      ZipEntry entry;
      while((entry = zin.getNextEntry())!=null){
         System.out.printf("File: %s Modified on %TD %n", 
         entry.getName(), new Date(entry.getTime()));
         extractFile(entry, zin); 
         System.out.printf("Zip file %s extracted successfully.", SOURCE_FILE);
         zin.closeEntry();
      }
      zin.close();
   }
   private static void extractFile(final ZipEntry entry, ZipInputStream is) 
      throws IOException {
      FileOutputStream fos = null; 
      try { 
         fos = new FileOutputStream(entry.getName()); 
         final byte[] buf = new byte[1024]; 
         int read = 0; 
         int length; 
         while ((length = is.read(buf, 0, buf.length)) >= 0) { 
            fos.write(buf, 0, length); 
         } 
      } catch (IOException ioex) { 
         fos.close(); 
      } 
   }
}

让我们编译并运行上面的程序,这将产生以下结果 -

File: D:\test\Hello.txt Modified on 05/22/17 
Zip file D:\test\Hello.txt extracted successfully.