org.apache.commons.lang.builder
クラス EqualsBuilder

java.lang.Object
  拡張org.apache.commons.lang.builder.EqualsBuilder

public class EqualsBuilder
extends Object

Assists in implementing Object.equals(Object) methods.

This class provides methods to build a good equals method for any class. It follows rules laid out in Effective Java , by Joshua Bloch. In particular the rule for comparing doubles, floats, and arrays can be tricky. Also, making sure that equals() and hashCode() are consistent can be difficult.

Two Objects that compare as equals must generate the same hash code, but two Objects with the same hash code do not have to be equal.

All relevant fields should be included in the calculation of equals. Derived fields may be ignored. In particular, any field used in generating a hash code must be used in the equals method, and vice versa.

Typical use for the code is as follows:

 public boolean equals(Object o) {
   if ( !(o instanceof MyClass) ) {
    return false;
   }
  MyClass rhs = (MyClass) o;
  return new EqualsBuilder()
                 .appendSuper(super.equals(o))
                 .append(field1, rhs.field1)
                 .append(field2, rhs.field2)
                 .append(field3, rhs.field3)
                 .isEquals();
  }
 

Alternatively, there is a method that uses reflection to determine the fields to test. Because these fields are usually private, the method, reflectionEquals, uses AccessibleObject.setAccessible to change the visibility of the fields. This will fail under a security manager, unless the appropriate permissions are set up correctly. It is also slower than testing explicitly.

A typical invocation for this method would look like:

 public boolean equals(Object o) {
   return EqualsBuilder.reflectionEquals(this, o);
 }
 

導入されたバージョン:
1.0
バージョン:
$Id: EqualsBuilder.java,v 1.1.1.1 2004/02/13 10:02:06 hioki Exp $
作成者:
Steve Downey, Stephen Colebourne, Gary Gregory, Pete Gieser

コンストラクタの概要
EqualsBuilder()
          Constructor for EqualsBuilder.
 
メソッドの概要
 EqualsBuilder append(boolean[] lhs, boolean[] rhs)
          Deep comparison of array of boolean.
 EqualsBuilder append(boolean lhs, boolean rhs)
          Test if two booleanss are equal.
 EqualsBuilder append(byte[] lhs, byte[] rhs)
          Deep comparison of array of byte.
 EqualsBuilder append(byte lhs, byte rhs)
          Test if two bytes are equal.
 EqualsBuilder append(char[] lhs, char[] rhs)
          Deep comparison of array of char.
 EqualsBuilder append(char lhs, char rhs)
          Test if two chars are equal.
 EqualsBuilder append(double[] lhs, double[] rhs)
          Deep comparison of array of double.
 EqualsBuilder append(double lhs, double rhs)
          Test if two doubles are equal by testing that the pattern of bits returned by doubleToLong are equal.
 EqualsBuilder append(float[] lhs, float[] rhs)
          Deep comparison of array of float.
 EqualsBuilder append(float lhs, float rhs)
          Test if two floats are equal byt testing that the pattern of bits returned by doubleToLong are equal.
 EqualsBuilder append(int[] lhs, int[] rhs)
          Deep comparison of array of int.
 EqualsBuilder append(int lhs, int rhs)
          Test if two ints are equal.
 EqualsBuilder append(long[] lhs, long[] rhs)
          Deep comparison of array of long.
 EqualsBuilder append(long lhs, long rhs)
          Test if two longs are equal.
 EqualsBuilder append(Object[] lhs, Object[] rhs)
          Performs a deep comparison of two Object arrays.
 EqualsBuilder append(Object lhs, Object rhs)
          Test if two Objects are equal using their equals method.
 EqualsBuilder append(short[] lhs, short[] rhs)
          Deep comparison of array of short.
 EqualsBuilder append(short lhs, short rhs)
          Test if two shorts are equal.
 EqualsBuilder appendSuper(boolean superEquals)
          Adds the result of super.equals() to this builder.
 boolean isEquals()
          Return true if the fields that have been checked are all equal.
static boolean reflectionEquals(Object lhs, Object rhs)
          This method uses reflection to determine if the two Objects are equal.
static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients)
          This method uses reflection to determine if the two Objects are equal.
static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class reflectUpToClass)
          This method uses reflection to determine if the two Objects are equal.
 
クラス java.lang.Object から継承したメソッド
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

コンストラクタの詳細

EqualsBuilder

public EqualsBuilder()

Constructor for EqualsBuilder.

Starts off assuming that equals is true.

関連項目:
Object.equals(java.lang.Object)
メソッドの詳細

reflectionEquals

public static boolean reflectionEquals(Object lhs,
                                       Object rhs)

This method uses reflection to determine if the two Objects are equal.

It uses AccessibleObject.setAccessible to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

Transient members will be not be tested, as they are likely derived fields, and not part of the value of the Object.

Static fields will not be tested. Superclass fields will be included.

パラメータ:
lhs - this object
rhs - the other object
戻り値:
true if the two Objects have tested equals.

reflectionEquals

public static boolean reflectionEquals(Object lhs,
                                       Object rhs,
                                       boolean testTransients)

This method uses reflection to determine if the two Objects are equal.

It uses AccessibleObject.setAccessible to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

If the TestTransients parameter is set to true, transient members will be tested, otherwise they are ignored, as they are likely derived fields, and not part of the value of the Object.

Static fields will not be tested. Superclass fields will be included.

パラメータ:
lhs - this object
rhs - the other object
testTransients - whether to include transient fields
戻り値:
true if the two Objects have tested equals.

reflectionEquals

public static boolean reflectionEquals(Object lhs,
                                       Object rhs,
                                       boolean testTransients,
                                       Class reflectUpToClass)

This method uses reflection to determine if the two Objects are equal.

It uses AccessibleObject.setAccessible to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

If the testTransients parameter is set to true, transient members will be tested, otherwise they are ignored, as they are likely derived fields, and not part of the value of the Object.

Static fields will not be included. Superclass fields will be appended up to and including the specified superclass. A null superclass is treated as java.lang.Object.

パラメータ:
lhs - this object
rhs - the other object
testTransients - whether to include transient fields
reflectUpToClass - the superclass to reflect up to (inclusive), may be null
戻り値:
true if the two Objects have tested equals.
導入されたバージョン:
2.0

appendSuper

public EqualsBuilder appendSuper(boolean superEquals)

Adds the result of super.equals() to this builder.

パラメータ:
superEquals - the result of calling super.equals()
戻り値:
EqualsBuilder - used to chain calls.
導入されたバージョン:
2.0

append

public EqualsBuilder append(Object lhs,
                            Object rhs)

Test if two Objects are equal using their equals method.

パラメータ:
lhs - the left hand object
rhs - the right hand object
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(long lhs,
                            long rhs)

Test if two longs are equal.

パラメータ:
lhs - the left hand long
rhs - the right hand long
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(int lhs,
                            int rhs)

Test if two ints are equal.

パラメータ:
lhs - the left hand int
rhs - the right hand int
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(short lhs,
                            short rhs)

Test if two shorts are equal.

パラメータ:
lhs - the left hand short
rhs - the right hand short
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(char lhs,
                            char rhs)

Test if two chars are equal.

パラメータ:
lhs - the left hand char
rhs - the right hand char
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(byte lhs,
                            byte rhs)

Test if two bytes are equal.

パラメータ:
lhs - the left hand byte
rhs - the right hand byte
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(double lhs,
                            double rhs)

Test if two doubles are equal by testing that the pattern of bits returned by doubleToLong are equal.

This handles NaNs, Infinties, and -0.0.

It is compatible with the hash code generated by HashCodeBuilder.

パラメータ:
lhs - the left hand double
rhs - the right hand double
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(float lhs,
                            float rhs)

Test if two floats are equal byt testing that the pattern of bits returned by doubleToLong are equal.

This handles NaNs, Infinties, and -0.0.

It is compatible with the hash code generated by HashCodeBuilder.

パラメータ:
lhs - the left hand float
rhs - the right hand float
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(boolean lhs,
                            boolean rhs)

Test if two booleanss are equal.

パラメータ:
lhs - the left hand boolean
rhs - the right hand boolean
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(Object[] lhs,
                            Object[] rhs)

Performs a deep comparison of two Object arrays.

This also will be called for the top level of multi-dimensional, ragged, and multi-typed arrays.

パラメータ:
lhs - the left hand Object[]
rhs - the right hand Object[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(long[] lhs,
                            long[] rhs)

Deep comparison of array of long. Length and all values are compared.

The method append(long, long) is used.

パラメータ:
lhs - the left hand long[]
rhs - the right hand long[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(int[] lhs,
                            int[] rhs)

Deep comparison of array of int. Length and all values are compared.

The method append(int, int) is used.

パラメータ:
lhs - the left hand int[]
rhs - the right hand int[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(short[] lhs,
                            short[] rhs)

Deep comparison of array of short. Length and all values are compared.

The method append(short, short) is used.

パラメータ:
lhs - the left hand short[]
rhs - the right hand short[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(char[] lhs,
                            char[] rhs)

Deep comparison of array of char. Length and all values are compared.

The method append(char, char) is used.

パラメータ:
lhs - the left hand char[]
rhs - the right hand char[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(byte[] lhs,
                            byte[] rhs)

Deep comparison of array of byte. Length and all values are compared.

The method append(byte, byte) is used.

パラメータ:
lhs - the left hand byte[]
rhs - the right hand byte[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(double[] lhs,
                            double[] rhs)

Deep comparison of array of double. Length and all values are compared.

The method append(double, double) is used.

パラメータ:
lhs - the left hand double[]
rhs - the right hand double[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(float[] lhs,
                            float[] rhs)

Deep comparison of array of float. Length and all values are compared.

The method append(float, float) is used.

パラメータ:
lhs - the left hand float[]
rhs - the right hand float[]
戻り値:
EqualsBuilder - used to chain calls.

append

public EqualsBuilder append(boolean[] lhs,
                            boolean[] rhs)

Deep comparison of array of boolean. Length and all values are compared.

The method append(boolean, boolean) is used.

パラメータ:
lhs - the left hand boolean[]
rhs - the right hand boolean[]
戻り値:
EqualsBuilder - used to chain calls.

isEquals

public boolean isEquals()

Return true if the fields that have been checked are all equal.

戻り値:
boolean


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