EqualsBuilder (Apache Commons Lang 3.20.0 API)
Description: declaration: package: org.apache.commons.lang3.builder, class: EqualsBuilder

# Class EqualsBuilder

java.lang.Object
org.apache.commons.lang3.builder.EqualsBuilder

All Implemented Interfaces:
  `Builder<Boolean>`

public class EqualsBuilder extends Object implements Builder<Boolean>
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 obj) {
      if (obj == null) { return false; }
      if (obj == this) { return true; }
      if (obj.getClass() != getClass()) {
        return false;
      }
      MyClass rhs = (MyClass) obj;
      return new EqualsBuilder()
                    .appendSuper(super.equals(obj))
                    .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. Non-primitive fields are compared using `equals()`.

A typical invocation for this method would look like:

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

The `EqualsExclude` annotation can be used to exclude fields from being used by the `reflectionEquals` methods.

Since:
  1.0

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `EqualsBuilder()`
  Constructor for EqualsBuilder.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `EqualsBuilder`
  `append(boolean[] lhs, boolean[] rhs)`
  Deep comparison of array of `boolean`.
  `EqualsBuilder`
  `append(boolean lhs, boolean rhs)`
  Test if two `booleans`s are equal.
  `EqualsBuilder`
  `append(byte[] lhs, byte[] rhs)`
  Deep comparison of array of `byte`.
  `EqualsBuilder`
  `append(byte lhs, byte rhs)`
  Test if two `byte`s are equal.
  `EqualsBuilder`
  `append(char[] lhs, char[] rhs)`
  Deep comparison of array of `char`.
  `EqualsBuilder`
  `append(char lhs, char rhs)`
  Test if two `char`s are equal.
  `EqualsBuilder`
  `append(double[] lhs, double[] rhs)`
  Deep comparison of array of `double`.
  `EqualsBuilder`
  `append(double lhs, double rhs)`
  Test if two `double`s 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 `float`s are equal by 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 `int`s are equal.
  `EqualsBuilder`
  `append(long[] lhs, long[] rhs)`
  Deep comparison of array of `long`.
  `EqualsBuilder`
  `append(long lhs, long rhs)`
  Test if two `long`s are equal.
  `EqualsBuilder`
  `append(short[] lhs, short[] rhs)`
  Deep comparison of array of `short`.
  `EqualsBuilder`
  `append(short lhs, short rhs)`
  Test if two `short`s 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 `Object`s are equal using either #`reflectionAppend(Object, Object)`, if object are non primitives (or wrapper of primitives) or if field `testRecursive` is set to `false`.
  `EqualsBuilder`
  `appendSuper(boolean superEquals)`
  Adds the result of `super.equals()` to this builder.
  `Boolean`
  `build()`
  Returns `true` if the fields that have been checked are all equal.
  `boolean`
  `isEquals()`
  Returns `true` if the fields that have been checked are all equal.
  `EqualsBuilder`
  `reflectionAppend(Object lhs, Object rhs)`
  Tests if two `objects` by using reflection.
  `static boolean`
  `reflectionEquals(Object lhs, Object rhs, boolean testTransients)`
  This method uses reflection to determine if the two `Object`s are equal.
  `static boolean`
  `reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class<?> reflectUpToClass, boolean testRecursive, String... excludeFields)`
  This method uses reflection to determine if the two `Object`s are equal.
  `static boolean`
  `reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class<?> reflectUpToClass, String... excludeFields)`
  This method uses reflection to determine if the two `Object`s are equal.
  `static boolean`
  `reflectionEquals(Object lhs, Object rhs, String... excludeFields)`
  This method uses reflection to determine if the two `Object`s are equal.
  `static boolean`
  `reflectionEquals(Object lhs, Object rhs, Collection<String> excludeFields)`
  This method uses reflection to determine if the two `Object`s are equal.
  `void`
  `reset()`
  Reset the EqualsBuilder so you can use the same object again.
  `EqualsBuilder`
  `setBypassReflectionClasses(List<Class<?>> bypassReflectionClasses)`
  Sets `Class`es whose instances should be compared by calling their `equals` although being in recursive mode.
  `protected void`
  `setEquals(boolean isEquals)`
  Sets the `isEquals` value.
  `EqualsBuilder`
  `setExcludeFields(String... excludeFields)`
  Sets field names to be excluded by reflection tests.
  `EqualsBuilder`
  `setReflectUpToClass(Class<?> reflectUpToClass)`
  Sets the superclass to reflect up to at reflective tests.
  `EqualsBuilder`
  `setTestRecursive(boolean testRecursive)`
  Sets whether to test fields recursively, instead of using their equals method, when reflectively comparing objects.
  `EqualsBuilder`
  `setTestTransients(boolean testTransients)`
  Sets whether to include transient fields when reflectively comparing objects.

  ### Methods inherited from class Object

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

- ## Constructor Details

  - ### EqualsBuilder

    public EqualsBuilder()
    Constructor for EqualsBuilder.

    Starts off assuming that equals is `true`.

    See Also:
      - `Object.equals(Object)`

- ## Method Details

  - ### reflectionEquals

    public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients)
    This method uses reflection to determine if the two `Object`s 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. Non-primitive fields are compared using `equals()`.

    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.

    Parameters:
      `lhs` - `this` object
      `rhs` - the other object
      `testTransients` - whether to include transient fields
    Returns:
      `true` if the two Objects have tested equals.
    See Also:
      - `EqualsExclude`

  - ### reflectionEquals

    public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class<?> reflectUpToClass, boolean testRecursive, String... excludeFields)
    This method uses reflection to determine if the two `Object`s 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. Non-primitive fields are compared using `equals()`.

    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.

    If the testRecursive parameter is set to `true`, non primitive (and non primitive wrapper) field types will be compared by `EqualsBuilder` recursively instead of invoking their `equals()` method. Leading to a deep reflection equals test.

    Parameters:
      `lhs` - `this` object
      `rhs` - the other object
      `testTransients` - whether to include transient fields
      `reflectUpToClass` - the superclass to reflect up to (inclusive), may be `null`
      `testRecursive` - whether to call reflection equals on non-primitive fields recursively.
      `excludeFields` - array of field names to exclude from testing
    Returns:
      `true` if the two Objects have tested equals.
    Since:
      3.6
    See Also:
      - `EqualsExclude`

  - ### reflectionEquals

    public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class<?> reflectUpToClass, String... excludeFields)
    This method uses reflection to determine if the two `Object`s 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. Non-primitive fields are compared using `equals()`.

    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.

    Parameters:
      `lhs` - `this` object
      `rhs` - the other object
      `testTransients` - whether to include transient fields
      `reflectUpToClass` - the superclass to reflect up to (inclusive), may be `null`
      `excludeFields` - array of field names to exclude from testing
    Returns:
      `true` if the two Objects have tested equals.
    Since:
      2.0
    See Also:
      - `EqualsExclude`

  - ### reflectionEquals

    public static boolean reflectionEquals(Object lhs, Object rhs, Collection<String> excludeFields)
    This method uses reflection to determine if the two `Object`s 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. Non-primitive fields are compared using `equals()`.

    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.

    Parameters:
      `lhs` - `this` object
      `rhs` - the other object
      `excludeFields` - Collection of String field names to exclude from testing
    Returns:
      `true` if the two Objects have tested equals.
    See Also:
      - `EqualsExclude`

  - ### reflectionEquals

    public static boolean reflectionEquals(Object lhs, Object rhs, String... excludeFields)
    This method uses reflection to determine if the two `Object`s 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. Non-primitive fields are compared using `equals()`.

    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.

    Parameters:
      `lhs` - `this` object
      `rhs` - the other object
      `excludeFields` - array of field names to exclude from testing
    Returns:
      `true` if the two Objects have tested equals.
    See Also:
      - `EqualsExclude`

  - ### append

    public EqualsBuilder append(boolean lhs, boolean rhs)
    Test if two `booleans`s are equal.
    Parameters:
      `lhs` - the left-hand side `boolean`
      `rhs` - the right-hand side `boolean`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `boolean[]`
      `rhs` - the right-hand side `boolean[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(byte lhs, byte rhs)
    Test if two `byte`s are equal.
    Parameters:
      `lhs` - the left-hand side `byte`
      `rhs` - the right-hand side `byte`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `byte[]`
      `rhs` - the right-hand side `byte[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(char lhs, char rhs)
    Test if two `char`s are equal.
    Parameters:
      `lhs` - the left-hand side `char`
      `rhs` - the right-hand side `char`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `char[]`
      `rhs` - the right-hand side `char[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(double lhs, double rhs)
    Test if two `double`s are equal by testing that the pattern of bits returned by `doubleToLong` are equal.

    This handles NaNs, Infinities, and `-0.0`.

    It is compatible with the hash code generated by `HashCodeBuilder`.

    Parameters:
      `lhs` - the left-hand side `double`
      `rhs` - the right-hand side `double`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `double[]`
      `rhs` - the right-hand side `double[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(float lhs, float rhs)
    Test if two `float`s are equal by testing that the pattern of bits returned by doubleToLong are equal.

    This handles NaNs, Infinities, and `-0.0`.

    It is compatible with the hash code generated by `HashCodeBuilder`.

    Parameters:
      `lhs` - the left-hand side `float`
      `rhs` - the right-hand side `float`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `float[]`
      `rhs` - the right-hand side `float[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(int lhs, int rhs)
    Test if two `int`s are equal.
    Parameters:
      `lhs` - the left-hand side `int`
      `rhs` - the right-hand side `int`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `int[]`
      `rhs` - the right-hand side `int[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(long lhs, long rhs)
    Test if two `long`s are equal.
    Parameters:
      `lhs` - the left-hand side `long`
      `rhs` - the right-hand side `long`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `long[]`
      `rhs` - the right-hand side `long[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(Object lhs, Object rhs)
    Test if two `Object`s are equal using either #`reflectionAppend(Object, Object)`, if object are non primitives (or wrapper of primitives) or if field `testRecursive` is set to `false`. Otherwise, using their `equals` method.
    Parameters:
      `lhs` - the left-hand side object
      `rhs` - the right-hand side object
    Returns:
      `this` instance.

  - ### 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.

    Note that this method does not compare the type of the arrays; it only compares the contents.

    Parameters:
      `lhs` - the left-hand side `Object[]`
      `rhs` - the right-hand side `Object[]`
    Returns:
      `this` instance.

  - ### append

    public EqualsBuilder append(short lhs, short rhs)
    Test if two `short`s are equal.
    Parameters:
      `lhs` - the left-hand side `short`
      `rhs` - the right-hand side `short`
    Returns:
      `this` instance.

  - ### 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.

    Parameters:
      `lhs` - the left-hand side `short[]`
      `rhs` - the right-hand side `short[]`
    Returns:
      `this` instance.

  - ### appendSuper

    public EqualsBuilder appendSuper(boolean superEquals)
    Adds the result of `super.equals()` to this builder.
    Parameters:
      `superEquals` - the result of calling `super.equals()`
    Returns:
      `this` instance.
    Since:
      2.0

  - ### build

    public Boolean build()
    Returns `true` if the fields that have been checked are all equal.
    Specified by:
      `build` in interface `Builder<Boolean>`
    Returns:
      `true` if all of the fields that have been checked are equal, `false` otherwise.
    Since:
      3.0

  - ### isEquals

    public boolean isEquals()
    Returns `true` if the fields that have been checked are all equal.
    Returns:
      boolean

  - ### reflectionAppend

    public EqualsBuilder reflectionAppend(Object lhs, Object rhs)
    Tests if two `objects` by using reflection.

    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. Non-primitive fields are compared using `equals()`.

    If the testTransients field 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 in field `reflectUpToClass`. A null superclass is treated as java.lang.Object.

    Field names listed in field `excludeFields` will be ignored.

    If either class of the compared objects is contained in `bypassReflectionClasses`, both objects are compared by calling the equals method of the left-hand side object with the right-hand side object as an argument.

    Parameters:
      `lhs` - the left-hand side object
      `rhs` - the right-hand side object
    Returns:
      `this` instance.

  - ### reset

    public void reset()
    Reset the EqualsBuilder so you can use the same object again.
    Since:
      2.5

  - ### setBypassReflectionClasses

    public EqualsBuilder setBypassReflectionClasses(List<Class<?>> bypassReflectionClasses)
    Sets `Class`es whose instances should be compared by calling their `equals` although being in recursive mode. So the fields of these classes will not be compared recursively by reflection.

    Here you should name classes having non-transient fields which are cache fields being set lazily.
    Prominent example being `String` class with its hash code cache field. Due to the importance of the `String` class, it is included in the default bypasses classes. Usually, if you use your own set of classes here, remember to include `String` class, too.

    Parameters:
      `bypassReflectionClasses` - classes to bypass reflection test
    Returns:
      `this` instance.
    Since:
      3.8
    See Also:
      - `setTestRecursive(boolean)`

  - ### setEquals

    protected void setEquals(boolean isEquals)
    Sets the `isEquals` value.
    Parameters:
      `isEquals` - The value to set.
    Since:
      2.1

  - ### setExcludeFields

    public EqualsBuilder setExcludeFields(String... excludeFields)
    Sets field names to be excluded by reflection tests.
    Parameters:
      `excludeFields` - the fields to exclude
    Returns:
      `this` instance.
    Since:
      3.6

  - ### setReflectUpToClass

    public EqualsBuilder setReflectUpToClass(Class<?> reflectUpToClass)
    Sets the superclass to reflect up to at reflective tests.
    Parameters:
      `reflectUpToClass` - the super class to reflect up to
    Returns:
      `this` instance.
    Since:
      3.6

  - ### setTestRecursive

    public EqualsBuilder setTestRecursive(boolean testRecursive)
    Sets whether to test fields recursively, instead of using their equals method, when reflectively comparing objects. String objects, which cache a hash value, are automatically excluded from recursive testing. You may specify other exceptions by calling `setBypassReflectionClasses(List)`.
    Parameters:
      `testRecursive` - whether to do a recursive test
    Returns:
      `this` instance.
    Since:
      3.6
    See Also:
      - `setBypassReflectionClasses(List)`

  - ### setTestTransients

    public EqualsBuilder setTestTransients(boolean testTransients)
    Sets whether to include transient fields when reflectively comparing objects.
    Parameters:
      `testTransients` - whether to test transient fields
    Returns:
      `this` instance.
    Since:
      3.6