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| Chapter 31 The java.util.zip Package |

## 31.4 java.util.zip.Checksum (JDK 1.1)

###

This interface defines the methods required to compute a checksum on a stream of data. The checksum is computed based on the bytes of data supplied by the `update()` methods, and the current value of the checksum can be obtained at any time with the `getValue()` method. `reset()` resets the checksum to its default value--use this method before beginning a new stream of data.

Note that the checksum value computed by a `Checksum` object and returned through the `getValue()` method must fit into a `long` value. Therefore, this interface is not suitable for the cryptographic checksum algorithms used in cryptography and security.

The classes `CheckedInputStream` and `CheckedOutputStream` provide a higher-level API for computing a checksum on a stream of data.

    public abstract interface Checksum {
        // Public Instance Methods
                public abstract long getValue();
                public abstract void reset();
                public abstract void update(int b);
                public abstract void update(byte[] b, int off, int len);
    }

### Implemented By:

Adler32, CRC32

### Passed To:

CheckedInputStream(), CheckedOutputStream()

### Returned By:

CheckedInputStream.getChecksum(), CheckedOutputStream.getChecksum()

java.util.zip.CheckedOutputStream (JDK 1.1) |  | java.util.zip.CRC32 (JDK 1.1)