[Chapter 18] CRC32

Synopsis

Class Name:

java.util.zip.CRC32

Superclass:

java.lang.Object

Immediate Subclasses:

None

Interfaces Implemented:

java.util.zip.Checksum

Availability:

New as of JDK 1.1

Description

The CRC32 class implements the Checksum interface using the CRC-32 algorithm. This algorithm is significantly slower than Adler-32 and only slightly more reliable.

Class Summary

public class java.util.zip.CRC32 extends java.lang.Object
             implements java.util.zip.Checksum {
  // Constructors
  public CRC32();
  
  // Instance Methods
  public long getValue();
  public void reset();
  public void update(int b);
  public void update(byte[] b);
  public native void update(byte[] b, int off, int len);
}

Constructors

CRC32

public CRC32()

Description: This constructor creates an CRC32 object.

Instance Methods

getValue

public long getValue()

Returns

The current checksum value.

Implements

Checksum.getValue()

Description

This method returns the current value of this checksum.

reset

public void reset()

Implements

Checksum.reset()

Description

This method resets the checksum to its initial value, making it appear as though it has not been updated by any data.

update

public void update(int b)

Parameters

b: The value to be added to the data stream for the checksum calculation.

Implements

Checksum.update(int)

Description

This method adds the specified value to the data stream and updates the checksum value. The method uses only the lowest eight bits of the given int.

public void update(byte[] b)

Parameters

b: An array of bytes to be added to the data stream for the checksum calculation.

Description

This method adds the bytes from the specified array to the data stream and updates the checksum value.

public native void update(byte[] b, int off, int len)

Parameters

b

An array of bytes to be added to the data stream for the checksum calculation.

off

An offset into the byte array.

len

The number of bytes to use.

Implements

Checksum.update(byte[], int, int)

Description

This method adds len bytes from the specified array, starting at off, to the data stream and updates the checksum value.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`equals(Object)`	`Object`
`finalize()`	`Object`	`getClass()`	`Object`
`hashCode()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`toString()`	`Object`
`wait()`	`Object`	`wait(long)`	`Object`
`wait(long, int)`	`Object`


Checksum		DataFormatException