Package org.apache.commons.lang3.builder

Class CompareToBuilder

  • All Implemented Interfaces:
    Builder<java.lang.Integer>
    public class CompareToBuilder
extends java.lang.Object
implements Builder<java.lang.Integer>
    Assists in implementing Comparable.compareTo(Object) methods.

    It is consistent with equals(Object) and hashcode() built with EqualsBuilder and HashCodeBuilder.

    Two Objects that compare equal using equals(Object) should normally also compare equal using compareTo(Object).

    All relevant fields should be included in the calculation of the comparison. Derived fields may be ignored. The same fields, in the same order, should be used in both compareTo(Object) and equals(Object).

    To use this class write code as follows:

     public class MyClass {
   String field1;
   int field2;
   boolean field3;

   ...

   public int compareTo(Object o) {
     MyClass myClass = (MyClass) o;
     return new CompareToBuilder()
       .appendSuper(super.compareTo(o)
       .append(this.field1, myClass.field1)
       .append(this.field2, myClass.field2)
       .append(this.field3, myClass.field3)
       .toComparison();
   }
 }

    Values are compared in the order they are appended to the builder. If any comparison returns a non-zero result, then that value will be the result returned by toComparison() and all subsequent comparisons are skipped.

    Alternatively, there are reflectionCompare methods that use reflection to determine the fields to append. Because fields can be private, reflectionCompare uses AccessibleObject.setAccessible(boolean) to bypass normal access control checks. This will fail under a security manager, unless the appropriate permissions are set up correctly. It is also slower than appending explicitly.

    A typical implementation of compareTo(Object) using reflectionCompare looks like:

     public int compareTo(Object o) {
   return CompareToBuilder.reflectionCompare(this, o);
 }

    The reflective methods compare object fields in the order returned by Class.getDeclaredFields(). The fields of the class are compared first, followed by those of its parent classes (in order from the bottom to the top of the class hierarchy).

    Since:
    1.0
    See Also:
    Comparable, Object.equals(Object), Object.hashCode(), EqualsBuilder, HashCodeBuilder

    • Constructor Summary

      Constructors 
      Constructor Description
      CompareToBuilder()
      Constructor for CompareToBuilder.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      CompareToBuilder append​(boolean[] lhs, boolean[] rhs)
      Appends to the builder the deep comparison of two boolean arrays.
      CompareToBuilder append​(boolean lhs, boolean rhs)
      Appends to the builder the comparison of two booleanss.
      CompareToBuilder append​(byte[] lhs, byte[] rhs)
      Appends to the builder the deep comparison of two byte arrays.
      CompareToBuilder append​(byte lhs, byte rhs)
      Appends to the builder the comparison of two bytes.
      CompareToBuilder append​(char[] lhs, char[] rhs)
      Appends to the builder the deep comparison of two char arrays.
      CompareToBuilder append​(char lhs, char rhs)
      Appends to the builder the comparison of two chars.
      CompareToBuilder append​(double[] lhs, double[] rhs)
      Appends to the builder the deep comparison of two double arrays.
      CompareToBuilder append​(double lhs, double rhs)
      Appends to the builder the comparison of two doubles.
      CompareToBuilder append​(float[] lhs, float[] rhs)
      Appends to the builder the deep comparison of two float arrays.
      CompareToBuilder append​(float lhs, float rhs)
      Appends to the builder the comparison of two floats.
      CompareToBuilder append​(int[] lhs, int[] rhs)
      Appends to the builder the deep comparison of two int arrays.
      CompareToBuilder append​(int lhs, int rhs)
      Appends to the builder the comparison of two ints.
      CompareToBuilder append​(long[] lhs, long[] rhs)
      Appends to the builder the deep comparison of two long arrays.
      CompareToBuilder append​(long lhs, long rhs)
      Appends to the builder the comparison of two longs.
      CompareToBuilder append​(short[] lhs, short[] rhs)
      Appends to the builder the deep comparison of two short arrays.
      CompareToBuilder append​(short lhs, short rhs)
      Appends to the builder the comparison of two shorts.
      CompareToBuilder append​(java.lang.Object[] lhs, java.lang.Object[] rhs)
      Appends to the builder the deep comparison of two Object arrays.
      CompareToBuilder append​(java.lang.Object[] lhs, java.lang.Object[] rhs, java.util.Comparator<?> comparator)
      Appends to the builder the deep comparison of two Object arrays.
      CompareToBuilder append​(java.lang.Object lhs, java.lang.Object rhs)
      Appends to the builder the comparison of two Objects.
      CompareToBuilder append​(java.lang.Object lhs, java.lang.Object rhs, java.util.Comparator<?> comparator)
      Appends to the builder the comparison of two Objects.
      CompareToBuilder appendSuper​(int superCompareTo)
      Appends to the builder the compareTo(Object) result of the superclass.
      java.lang.Integer build()
      Returns a negative Integer, a positive Integer, or zero as the builder has judged the "left-hand" side as less than, greater than, or equal to the "right-hand" side.
      static int reflectionCompare​(java.lang.Object lhs, java.lang.Object rhs)
      Compares two Objects via reflection.
      static int reflectionCompare​(java.lang.Object lhs, java.lang.Object rhs, boolean compareTransients)
      Compares two Objects via reflection.
      static int reflectionCompare​(java.lang.Object lhs, java.lang.Object rhs, boolean compareTransients, java.lang.Class<?> reflectUpToClass, java.lang.String... excludeFields)
      Compares two Objects via reflection.
      static int reflectionCompare​(java.lang.Object lhs, java.lang.Object rhs, java.lang.String... excludeFields)
      Compares two Objects via reflection.
      static int reflectionCompare​(java.lang.Object lhs, java.lang.Object rhs, java.util.Collection<java.lang.String> excludeFields)
      Compares two Objects via reflection.
      int toComparison()
      Returns a negative integer, a positive integer, or zero as the builder has judged the "left-hand" side as less than, greater than, or equal to the "right-hand" side.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • CompareToBuilder

        public CompareToBuilder()

        Constructor for CompareToBuilder.

        Starts off assuming that the objects are equal. Multiple calls are then made to the various append methods, followed by a call to toComparison() to get the result.

    • Method Detail

      • reflectionCompare

        public static int reflectionCompare​(java.lang.Object lhs,
                                    java.lang.Object rhs)

        Compares two Objects via reflection.

        Fields can be private, thus AccessibleObject.setAccessible is used to bypass normal access control checks. This will fail under a security manager unless the appropriate permissions are set.

        • Static fields will not be compared
        • Transient members will be not be compared, as they are likely derived fields
        • Superclass fields will be compared

        If both lhs and rhs are null, they are considered equal.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        Returns:
        a negative integer, zero, or a positive integer as lhs is less than, equal to, or greater than rhs
        Throws:
        java.lang.NullPointerException - if either (but not both) parameters are null
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs

      • reflectionCompare

        public static int reflectionCompare​(java.lang.Object lhs,
                                    java.lang.Object rhs,
                                    boolean compareTransients)

        Compares two Objects via reflection.

        Fields can be private, thus AccessibleObject.setAccessible is used to bypass normal access control checks. This will fail under a security manager unless the appropriate permissions are set.

        • Static fields will not be compared
        • If compareTransients is true, compares transient members. Otherwise ignores them, as they are likely derived fields.
        • Superclass fields will be compared

        If both lhs and rhs are null, they are considered equal.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        compareTransients - whether to compare transient fields
        Returns:
        a negative integer, zero, or a positive integer as lhs is less than, equal to, or greater than rhs
        Throws:
        java.lang.NullPointerException - if either lhs or rhs (but not both) is null
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs

      • reflectionCompare

        public static int reflectionCompare​(java.lang.Object lhs,
                                    java.lang.Object rhs,
                                    java.util.Collection<java.lang.String> excludeFields)

        Compares two Objects via reflection.

        Fields can be private, thus AccessibleObject.setAccessible is used to bypass normal access control checks. This will fail under a security manager unless the appropriate permissions are set.

        • Static fields will not be compared
        • If compareTransients is true, compares transient members. Otherwise ignores them, as they are likely derived fields.
        • Superclass fields will be compared

        If both lhs and rhs are null, they are considered equal.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        excludeFields - Collection of String fields to exclude
        Returns:
        a negative integer, zero, or a positive integer as lhs is less than, equal to, or greater than rhs
        Throws:
        java.lang.NullPointerException - if either lhs or rhs (but not both) is null
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs
        Since:
        2.2

      • reflectionCompare

        public static int reflectionCompare​(java.lang.Object lhs,
                                    java.lang.Object rhs,
                                    java.lang.String... excludeFields)

        Compares two Objects via reflection.

        Fields can be private, thus AccessibleObject.setAccessible is used to bypass normal access control checks. This will fail under a security manager unless the appropriate permissions are set.

        • Static fields will not be compared
        • If compareTransients is true, compares transient members. Otherwise ignores them, as they are likely derived fields.
        • Superclass fields will be compared

        If both lhs and rhs are null, they are considered equal.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        excludeFields - array of fields to exclude
        Returns:
        a negative integer, zero, or a positive integer as lhs is less than, equal to, or greater than rhs
        Throws:
        java.lang.NullPointerException - if either lhs or rhs (but not both) is null
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs
        Since:
        2.2

      • reflectionCompare

        public static int reflectionCompare​(java.lang.Object lhs,
                                    java.lang.Object rhs,
                                    boolean compareTransients,
                                    java.lang.Class<?> reflectUpToClass,
                                    java.lang.String... excludeFields)

        Compares two Objects via reflection.

        Fields can be private, thus AccessibleObject.setAccessible is used to bypass normal access control checks. This will fail under a security manager unless the appropriate permissions are set.

        • Static fields will not be compared
        • If the compareTransients is true, compares transient members. Otherwise ignores them, as they are likely derived fields.
        • Compares superclass fields up to and including reflectUpToClass. If reflectUpToClass is null, compares all superclass fields.

        If both lhs and rhs are null, they are considered equal.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        compareTransients - whether to compare transient fields
        reflectUpToClass - last superclass for which fields are compared
        excludeFields - fields to exclude
        Returns:
        a negative integer, zero, or a positive integer as lhs is less than, equal to, or greater than rhs
        Throws:
        java.lang.NullPointerException - if either lhs or rhs (but not both) is null
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs
        Since:
        2.2 (2.0 as reflectionCompare(Object, Object, boolean, Class))

      • appendSuper

        public CompareToBuilder appendSuper​(int superCompareTo)

        Appends to the builder the compareTo(Object) result of the superclass.

        Parameters:
        superCompareTo - result of calling super.compareTo(Object)
        Returns:
        this - used to chain append calls
        Since:
        2.0

      • append

        public CompareToBuilder append​(java.lang.Object lhs,
                               java.lang.Object rhs)

        Appends to the builder the comparison of two Objects.

        1. Check if lhs == rhs
        2. Check if either lhs or rhs is null, a null object is less than a non-null object
        3. Check the object contents

        lhs must either be an array or implement Comparable.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        Returns:
        this - used to chain append calls
        Throws:
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs

      • append

        public CompareToBuilder append​(java.lang.Object lhs,
                               java.lang.Object rhs,
                               java.util.Comparator<?> comparator)

        Appends to the builder the comparison of two Objects.

        1. Check if lhs == rhs
        2. Check if either lhs or rhs is null, a null object is less than a non-null object
        3. Check the object contents

        If lhs is an array, array comparison methods will be used. Otherwise comparator will be used to compare the objects. If comparator is null, lhs must implement Comparable instead.

        Parameters:
        lhs - left-hand object
        rhs - right-hand object
        comparator - Comparator used to compare the objects, null means treat lhs as Comparable
        Returns:
        this - used to chain append calls
        Throws:
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs
        Since:
        2.0

      • append

        public CompareToBuilder append​(long lhs,
                               long rhs)
        Appends to the builder the comparison of two longs.
        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(int lhs,
                               int rhs)
        Appends to the builder the comparison of two ints.
        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(short lhs,
                               short rhs)
        Appends to the builder the comparison of two shorts.
        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(char lhs,
                               char rhs)
        Appends to the builder the comparison of two chars.
        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(byte lhs,
                               byte rhs)
        Appends to the builder the comparison of two bytes.
        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(double lhs,
                               double rhs)

        Appends to the builder the comparison of two doubles.

        This handles NaNs, Infinities, and -0.0.

        It is compatible with the hash code generated by HashCodeBuilder.

        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(float lhs,
                               float rhs)

        Appends to the builder the comparison of two floats.

        This handles NaNs, Infinities, and -0.0.

        It is compatible with the hash code generated by HashCodeBuilder.

        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(boolean lhs,
                               boolean rhs)
        Appends to the builder the comparison of two booleanss.
        Parameters:
        lhs - left-hand value
        rhs - right-hand value
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(java.lang.Object[] lhs,
                               java.lang.Object[] rhs)

        Appends to the builder the deep comparison of two Object arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a short length array is less than a long length array
        4. Check array contents element by element using append(Object, Object, Comparator)

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

        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls
        Throws:
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs

      • append

        public CompareToBuilder append​(java.lang.Object[] lhs,
                               java.lang.Object[] rhs,
                               java.util.Comparator<?> comparator)

        Appends to the builder the deep comparison of two Object arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a short length array is less than a long length array
        4. Check array contents element by element using append(Object, Object, Comparator)

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

        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        comparator - Comparator to use to compare the array elements, null means to treat lhs elements as Comparable.
        Returns:
        this - used to chain append calls
        Throws:
        java.lang.ClassCastException - if rhs is not assignment-compatible with lhs
        Since:
        2.0

      • append

        public CompareToBuilder append​(long[] lhs,
                               long[] rhs)

        Appends to the builder the deep comparison of two long arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(long, long)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(int[] lhs,
                               int[] rhs)

        Appends to the builder the deep comparison of two int arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(int, int)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(short[] lhs,
                               short[] rhs)

        Appends to the builder the deep comparison of two short arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(short, short)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(char[] lhs,
                               char[] rhs)

        Appends to the builder the deep comparison of two char arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(char, char)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(byte[] lhs,
                               byte[] rhs)

        Appends to the builder the deep comparison of two byte arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(byte, byte)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(double[] lhs,
                               double[] rhs)

        Appends to the builder the deep comparison of two double arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(double, double)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(float[] lhs,
                               float[] rhs)

        Appends to the builder the deep comparison of two float arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(float, float)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • append

        public CompareToBuilder append​(boolean[] lhs,
                               boolean[] rhs)

        Appends to the builder the deep comparison of two boolean arrays.

        1. Check if arrays are the same using ==
        2. Check if for null, null is less than non-null
        3. Check array length, a shorter length array is less than a longer length array
        4. Check array contents element by element using append(boolean, boolean)
        Parameters:
        lhs - left-hand array
        rhs - right-hand array
        Returns:
        this - used to chain append calls

      • toComparison

        public int toComparison()
        Returns a negative integer, a positive integer, or zero as the builder has judged the "left-hand" side as less than, greater than, or equal to the "right-hand" side.
        Returns:
        final comparison result
        See Also:
        build()

      • build

        public java.lang.Integer build()
        Returns a negative Integer, a positive Integer, or zero as the builder has judged the "left-hand" side as less than, greater than, or equal to the "right-hand" side.
        Specified by:
        build in interface Builder<java.lang.Integer>
        Returns:
        final comparison result as an Integer
        Since:
        3.0
        See Also:
        toComparison()