Package 

Class ObjectUtils

  • 
public class ObjectUtils

    Operations on {@code Object}.

    This class tries to handle {@code null} input gracefully. An exception will generally not be thrown for a {@code null} input. Each method documents its behaviour in more detail.

    #ThreadSafe#

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      public class ObjectUtils.Null

      Class used as a null placeholder where {@code null} has another meaning.

      For example, in a {@code HashMap} the get method returns {@code null} if the {@code Map} contains {@code null} or if there isno matching key. The {@code Null} placeholder can be used to distinguishbetween these two cases.

      Another example is {@code Hashtable}, where {@code null} cannot be stored.

    • Constructor Summary

      Constructors 
      Constructor Description
      ObjectUtils() {@code ObjectUtils} instances should NOT be constructed instandard programming.

    • Method Summary

      Modifier and Type Method Description
      static <T> T defaultIfNull(T object, T defaultValue) Returns a default value if the object passed is {@code null}.
      static <T> T firstNonNull(Array<T> values) Returns the first value in the array which is not {@code null}.
      static boolean equals(Object object1, Object object2) Compares two objects for equality, where either one or bothobjects may be {@code null}.
      static boolean notEqual(Object object1, Object object2) Compares two objects for inequality, where either one or bothobjects may be {@code null}.
      static int hashCode(Object obj) Gets the hash code of an object returning zero when theobject is {@code null}.
      static int hashCodeMulti(Array<Object> objects) Gets the hash code for multiple objects.
      static String identityToString(Object object) Gets the toString that would be produced by {@code Object} if a class did not override toString itself.
      static void identityToString(StringBuffer buffer, Object object) Appends the toString that would be produced by {@code Object} if a class did not override toString itself.
      static String toString(Object obj) Gets the {@code toString} of an {@code Object} returningan empty string ("") if {@code null} input.
      static String toString(Object obj, String nullStr) Gets the {@code toString} of an {@code Object} returninga specified text if {@code null} input.
      static <T extends Comparable<out Object>> T min(Array<T> values) Null safe comparison of Comparables.
      static <T extends Comparable<out Object>> T max(Array<T> values) Null safe comparison of Comparables.
      static <T extends Comparable<out Object>> int compare(T c1, T c2) Null safe comparison of Comparables.
      static <T extends Comparable<out Object>> int compare(T c1, T c2, boolean nullGreater) Null safe comparison of Comparables.
      static <T extends Comparable<out Object>> T median(Array<T> items) Find the "best guess" middle value among comparables.
      static <T> T median(Comparator<T> comparator, Array<T> items) Find the "best guess" middle value among comparables.
      static <T> T mode(Array<T> items) Find the most frequently occurring item.
      static <T> T clone(T obj) Clone an object.
      static <T> T cloneIfPossible(T obj) Clone an object if possible.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • ObjectUtils

        ObjectUtils()
        {@code ObjectUtils} instances should NOT be constructed instandard programming.

    • Method Detail

      • defaultIfNull

         static <T> T defaultIfNull(T object, T defaultValue)

        Returns a default value if the object passed is {@code null}.

        ObjectUtils.defaultIfNull(null, null)      = null
ObjectUtils.defaultIfNull(null, "")        = ""
ObjectUtils.defaultIfNull(null, "zz")      = "zz"
ObjectUtils.defaultIfNull("abc", *)        = "abc"
ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE
        Parameters:
        object - the {@code Object} to test, may be {@code null}
        defaultValue - the default value to return, may be {@code null}

      • firstNonNull

         static <T> T firstNonNull(Array<T> values)

        Returns the first value in the array which is not {@code null}.If all the values are {@code null} or the array is {@code null} or empty then {@code null} is returned.

        ObjectUtils.firstNonNull(null, null)      = null
ObjectUtils.firstNonNull(null, "")        = ""
ObjectUtils.firstNonNull(null, null, "")  = ""
ObjectUtils.firstNonNull(null, "zz")      = "zz"
ObjectUtils.firstNonNull("abc", *)        = "abc"
ObjectUtils.firstNonNull(null, "xyz", *)  = "xyz"
ObjectUtils.firstNonNull(Boolean.TRUE, *) = Boolean.TRUE
ObjectUtils.firstNonNull()                = null
        Parameters:
        values - the values to test, may be {@code null} or empty

      • equals

         static boolean equals(Object object1, Object object2)

        Compares two objects for equality, where either one or bothobjects may be {@code null}.

        ObjectUtils.equals(null, null)                  = true
ObjectUtils.equals(null, "")                    = false
ObjectUtils.equals("", null)                    = false
ObjectUtils.equals("", "")                      = true
ObjectUtils.equals(Boolean.TRUE, null)          = false
ObjectUtils.equals(Boolean.TRUE, "true")        = false
ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE)  = true
ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false
        Parameters:
        object1 - the first object, may be {@code null}
        object2 - the second object, may be {@code null}

      • notEqual

         static boolean notEqual(Object object1, Object object2)

        Compares two objects for inequality, where either one or bothobjects may be {@code null}.

        ObjectUtils.notEqual(null, null)                  = false
ObjectUtils.notEqual(null, "")                    = true
ObjectUtils.notEqual("", null)                    = true
ObjectUtils.notEqual("", "")                      = false
ObjectUtils.notEqual(Boolean.TRUE, null)          = true
ObjectUtils.notEqual(Boolean.TRUE, "true")        = true
ObjectUtils.notEqual(Boolean.TRUE, Boolean.TRUE)  = false
ObjectUtils.notEqual(Boolean.TRUE, Boolean.FALSE) = true
        Parameters:
        object1 - the first object, may be {@code null}
        object2 - the second object, may be {@code null}

      • hashCode

         static int hashCode(Object obj)

        Gets the hash code of an object returning zero when theobject is {@code null}.

        ObjectUtils.hashCode(null)   = 0
ObjectUtils.hashCode(obj)    = obj.hashCode()
        Parameters:
        obj - the object to obtain the hash code of, may be {@code null}

      • hashCodeMulti

         static int hashCodeMulti(Array<Object> objects)

        Gets the hash code for multiple objects.

        This allows a hash code to be rapidly calculated for a number of objects.The hash code for a single object is the not same as hashCode.The hash code for multiple objects is the same as that calculated by an {@code ArrayList} containing the specified objects.

        ObjectUtils.hashCodeMulti()                 = 1
ObjectUtils.hashCodeMulti((Object[]) null)  = 1
ObjectUtils.hashCodeMulti(a)                = 31 + a.hashCode()
ObjectUtils.hashCodeMulti(a,b)              = (31 + a.hashCode()) * 31 + b.hashCode()
ObjectUtils.hashCodeMulti(a,b,c)            = ((31 + a.hashCode()) * 31 + b.hashCode()) * 31 + c.hashCode()
        Parameters:
        objects - the objects to obtain the hash code of, may be {@code null}

      • identityToString

         static String identityToString(Object object)

        Gets the toString that would be produced by {@code Object} if a class did not override toString itself. {@code null} will return {@code null}.

        ObjectUtils.identityToString(null)         = null
ObjectUtils.identityToString("")           = "java.lang.String@1e23"
ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa"
        Parameters:
        object - the object to create a toString for, may be{@code null}

      • identityToString

         static void identityToString(StringBuffer buffer, Object object)

        Appends the toString that would be produced by {@code Object} if a class did not override toString itself. {@code null} will throw a NullPointerException for either of the two parameters. 

        ObjectUtils.identityToString(buf, "")            = buf.append("java.lang.String@1e23"
ObjectUtils.identityToString(buf, Boolean.TRUE)  = buf.append("java.lang.Boolean@7fa"
ObjectUtils.identityToString(buf, Boolean.TRUE)  = buf.append("java.lang.Boolean@7fa")
        Parameters:
        buffer - the buffer to append to
        object - the object to create a toString for

      • toString

         static String toString(Object obj)

        Gets the {@code toString} of an {@code Object} returningan empty string ("") if {@code null} input.

        ObjectUtils.toString(null)         = ""
ObjectUtils.toString("")           = ""
ObjectUtils.toString("bat")        = "bat"
ObjectUtils.toString(Boolean.TRUE) = "true"
        Parameters:
        obj - the Object to {@code toString}, may be null

      • toString

         static String toString(Object obj, String nullStr)

        Gets the {@code toString} of an {@code Object} returninga specified text if {@code null} input.

        ObjectUtils.toString(null, null)           = null
ObjectUtils.toString(null, "null")         = "null"
ObjectUtils.toString("", "null")           = ""
ObjectUtils.toString("bat", "null")        = "bat"
ObjectUtils.toString(Boolean.TRUE, "null") = "true"
        Parameters:
        obj - the Object to {@code toString}, may be null
        nullStr - the String to return if {@code null} input, may be null

      • min

         static <T extends Comparable<out Object>> T min(Array<T> values)

        Null safe comparison of Comparables.

        Parameters:
        values - the set of comparable values, may be null

      • max

         static <T extends Comparable<out Object>> T max(Array<T> values)

        Null safe comparison of Comparables.

        Parameters:
        values - the set of comparable values, may be null

      • compare

         static <T extends Comparable<out Object>> int compare(T c1, T c2)

        Null safe comparison of Comparables. {@code null} is assumed to be less than a non-{@code null} value.

        Parameters:
        c1 - the first comparable, may be null
        c2 - the second comparable, may be null

      • compare

         static <T extends Comparable<out Object>> int compare(T c1, T c2, boolean nullGreater)

        Null safe comparison of Comparables.

        Parameters:
        c1 - the first comparable, may be null
        c2 - the second comparable, may be null
        nullGreater - if true {@code null} is considered greaterthan a non-{@code null} value or if false {@code null} isconsidered less than a Non-{@code null} value

      • median

         static <T extends Comparable<out Object>> T median(Array<T> items)

        Find the "best guess" middle value among comparables. If there is an evennumber of total values, the lower of the two middle values will be returned.

        Parameters:
        items - to compare

      • median

         static <T> T median(Comparator<T> comparator, Array<T> items)

        Find the "best guess" middle value among comparables. If there is an evennumber of total values, the lower of the two middle values will be returned.

        Parameters:
        comparator - to use for comparisons
        items - to compare

      • mode

         static <T> T mode(Array<T> items)

        Find the most frequently occurring item.

        Parameters:
        items - to check

      • clone

         static <T> T clone(T obj)

        Clone an object.

        Parameters:
        obj - the object to clone, null returns null

      • cloneIfPossible

         static <T> T cloneIfPossible(T obj)

        Clone an object if possible.

        This method is similar to clone, but will return the providedinstance as the return value instead of {@code null} if the instanceis not cloneable. This is more convenient if the caller uses differentimplementations (e.g. of a service) and some of the implementations do not allow concurrentprocessing or have state. In such cases the implementation can simply provide a properclone implementation and the caller's code does not have to change.

        Parameters:
        obj - the object to clone, null returns null