com.itextpdf.awt.geom.misc

Class HashCode

java.lang.Object

com.itextpdf.awt.geom.misc.HashCode

public final class HashCode
extends Object

This class is a convenience method to sequentially calculate hash code of the object based on the field values. The result depends on the order of elements appended. The exact formula is the same as for java.util.List.hashCode. If you need order independent hash code just summate, multiply or XOR all elements.

Suppose we have class:

 class Thing {
     long id;
     String name;
     float weight;
 }
 

The hash code calculation can be expressed in 2 forms.

For maximum performance:

 public int hashCode() {
     int hashCode = HashCode.EMPTY_HASH_CODE;
     hashCode = HashCode.combine(hashCode, id);
     hashCode = HashCode.combine(hashCode, name);
     hashCode = HashCode.combine(hashCode, weight);
     return hashCode;
 }
 

For convenience:

 public int hashCode() {
     return new HashCode().append(id).append(name).append(weight).hashCode();
 }
 

See Also:

List.hashCode()

Field Summary

Fields

Modifier and Type	Field and Description
static int	EMPTY_HASH_CODE The hashCode value before any data is appended, equals to 1.

Constructor Summary

Constructors

Constructor and Description
HashCode()

Method Summary

Modifier and Type	Method and Description
HashCode	append(boolean value) Appends value's hashCode to the current hashCode.
HashCode	append(double value) Appends value's hashCode to the current hashCode.
HashCode	append(float value) Appends value's hashCode to the current hashCode.
HashCode	append(int value) Appends value's hashCode to the current hashCode.
HashCode	append(long value) Appends value's hashCode to the current hashCode.
HashCode	append(Object value) Appends value's hashCode to the current hashCode.
static int	combine(int hashCode, boolean value) Combines hashCode of previous elements sequence and value's hashCode.
static int	combine(int hashCode, double value) Combines hashCode of previous elements sequence and value's hashCode.
static int	combine(int hashCode, float value) Combines hashCode of previous elements sequence and value's hashCode.
static int	combine(int hashCode, int value) Combines hashCode of previous elements sequence and value's hashCode.
static int	combine(int hashCode, long value) Combines hashCode of previous elements sequence and value's hashCode.
static int	combine(int hashCode, Object value) Combines hashCode of previous elements sequence and value's hashCode.
int	hashCode() Returns accumulated hashCode

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

EMPTY_HASH_CODE

public static final int EMPTY_HASH_CODE

The hashCode value before any data is appended, equals to 1.

See Also:

List.hashCode(), Constant Field Values

Constructor Detail

HashCode

public HashCode()

Method Detail

hashCode

public final int hashCode()

Returns accumulated hashCode

Overrides:

hashCode in class Object

combine

public static int combine(int hashCode,
                          boolean value)

Combines hashCode of previous elements sequence and value's hashCode.

Parameters:

hashCode - previous hashCode value

value - new element

Returns:

combined hashCode

combine

public static int combine(int hashCode,
                          long value)

Combines hashCode of previous elements sequence and value's hashCode.

Parameters:

hashCode - previous hashCode value

value - new element

Returns:

combined hashCode

combine

public static int combine(int hashCode,
                          float value)

Combines hashCode of previous elements sequence and value's hashCode.

Parameters:

hashCode - previous hashCode value

value - new element

Returns:

combined hashCode

combine

public static int combine(int hashCode,
                          double value)

Combines hashCode of previous elements sequence and value's hashCode.

Parameters:

hashCode - previous hashCode value

value - new element

Returns:

combined hashCode

combine

public static int combine(int hashCode,
                          Object value)

Combines hashCode of previous elements sequence and value's hashCode.

Parameters:

hashCode - previous hashCode value

value - new element

Returns:

combined hashCode

combine

public static int combine(int hashCode,
                          int value)

Combines hashCode of previous elements sequence and value's hashCode.

Parameters:

hashCode - previous hashCode value

value - new element

Returns:

combined hashCode

append

public final HashCode append(int value)

Appends value's hashCode to the current hashCode.

Parameters:

value - new element

Returns:

this

append

public final HashCode append(long value)

Appends value's hashCode to the current hashCode.

Parameters:

value - new element

Returns:

this

append

public final HashCode append(float value)

Appends value's hashCode to the current hashCode.

Parameters:

value - new element

Returns:

this

append

public final HashCode append(double value)

Appends value's hashCode to the current hashCode.

Parameters:

value - new element

Returns:

this

append

public final HashCode append(boolean value)

Appends value's hashCode to the current hashCode.

Parameters:

value - new element

Returns:

this

append

public final HashCode append(Object value)

Appends value's hashCode to the current hashCode.

Parameters:

value - new element

Returns:

this