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| Chapter 31 |

# 31. The java.util.zip Package

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The `java.util.zip` package contains classes for data compression and decompression. It is new in Java 1.1. Figure 31.1 shows the class hierarchy of the package.

The `Deflater` and `Inflater` classes perform data compression and decompression. `DeflaterOutputStream` and `InflaterInputStream` apply that functionality to byte streams; the subclasses of these streams implement both the GZIP and ZIP compression formats. The `Adler32` and `CRC32` classes implement the `Checksum` interface and compute the checksums required for data compression.

#### Figure 31.1: The java.util.zip package

## 31.1 java.util.zip.Adler32 (JDK 1.1)

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This class implements the `Checksum` interface and computes a checksum on a stream of data using the Adler-32 algorithm. This algorithm is significantly faster than the CRC-32 algorithm and is almost as reliable.

The `CheckedInputStream` and `CheckedOutputStream` classes provide a higher-level interface to computing checksums on streams of data.

    public class Adler32 extends Object implements Checksum {
        // Default Constructor: public Adler32()
        // Public Instance Methods
                public long getValue();  // From Checksum
                public void reset();  // From Checksum
                public void update(int b);  // From Checksum
                public native void update(byte[] b, int off, int len);  // From Checksum
                public void update(byte[] b);
    }

java.util.Vector (JDK 1.0) |  | java.util.zip.CheckedInputStream (JDK 1.1)