Class ObjectUtils

java.lang.Object
org.apache.commons.lang3.ObjectUtils

public class ObjectUtils extends Object

Operations on Object.

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

#ThreadSafe#

Since:
1.0
  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    Class used as a null placeholder where null has another meaning.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final ObjectUtils.Null
    Singleton used as a null placeholder where null has another meaning.
  • Constructor Summary

    Constructors
    Constructor
    Description
    ObjectUtils instances should NOT be constructed in standard programming.
  • Method Summary

    Modifier and Type
    Method
    Description
    static boolean
    allNotNull(Object... values)
    Checks if all values in the array are not nulls.
    static boolean
    anyNotNull(Object... values)
    Checks if any value in the given array is not null.
    static <T> T
    clone(T obj)
    Clone an object.
    static <T> T
    Clone an object if possible.
    static <T extends Comparable<? super T>>
    int
    compare(T c1, T c2)
    Null safe comparison of Comparables.
    static <T extends Comparable<? super T>>
    int
    compare(T c1, T c2, boolean nullGreater)
    Null safe comparison of Comparables.
    static boolean
    CONST(boolean v)
    This method returns the provided value unchanged.
    static byte
    CONST(byte v)
    This method returns the provided value unchanged.
    static char
    CONST(char v)
    This method returns the provided value unchanged.
    static double
    CONST(double v)
    This method returns the provided value unchanged.
    static float
    CONST(float v)
    This method returns the provided value unchanged.
    static int
    CONST(int v)
    This method returns the provided value unchanged.
    static long
    CONST(long v)
    This method returns the provided value unchanged.
    static short
    CONST(short v)
    This method returns the provided value unchanged.
    static <T> T
    CONST(T v)
    This method returns the provided value unchanged.
    static byte
    CONST_BYTE(int v)
    This method returns the provided value unchanged.
    static short
    CONST_SHORT(int v)
    This method returns the provided value unchanged.
    static <T> T
    defaultIfNull(T object, T defaultValue)
    Returns a default value if the object passed is null.
    static boolean
    equals(Object object1, Object object2)
    Deprecated.
    this method has been replaced by java.util.Objects.equals(Object, Object) in Java 7 and will be removed from future releases.
    static <T> T
    firstNonNull(T... values)
    Returns the first value in the array which is not null.
    static int
    Deprecated.
    this method has been replaced by java.util.Objects.hashCode(Object) in Java 7 and will be removed in future releases
    static int
    hashCodeMulti(Object... objects)
    Deprecated.
    this method has been replaced by java.util.Objects.hash(Object...) in Java 7 and will be removed in future releases.
    static void
    identityToString(Appendable appendable, Object object)
    Appends the toString that would be produced by Object if a class did not override toString itself.
    static String
    Gets the toString that would be produced by Object if a class did not override toString itself.
    static void
    Appends the toString that would be produced by Object if a class did not override toString itself.
    static void
    Appends the toString that would be produced by Object if a class did not override toString itself.
    static void
    Deprecated.
    as of 3.6, because StrBuilder was moved to commons-text, use one of the other identityToString methods instead
    static <T extends Comparable<? super T>>
    T
    max(T... values)
    Null safe comparison of Comparables.
    static <T> T
    median(Comparator<T> comparator, T... items)
    Find the "best guess" middle value among comparables.
    static <T extends Comparable<? super T>>
    T
    median(T... items)
    Find the "best guess" middle value among comparables.
    static <T extends Comparable<? super T>>
    T
    min(T... values)
    Null safe comparison of Comparables.
    static <T> T
    mode(T... items)
    Find the most frequently occurring item.
    static boolean
    notEqual(Object object1, Object object2)
    Compares two objects for inequality, where either one or both objects may be null.
    static String
    Deprecated.
    this method has been replaced by java.util.Objects.toString(Object) in Java 7 and will be removed in future releases.
    static String
    toString(Object obj, String nullStr)
    Deprecated.
    this method has been replaced by java.util.Objects.toString(Object, String) in Java 7 and will be removed in future releases.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • NULL

      public static final ObjectUtils.Null NULL

      Singleton used as a null placeholder where null has another meaning.

      For example, in a HashMap the HashMap.get(java.lang.Object) method returns null if the Map contains null or if there is no matching key. The Null placeholder can be used to distinguish between these two cases.

      Another example is Hashtable, where null cannot be stored.

      This instance is Serializable.

  • Constructor Details

    • ObjectUtils

      public ObjectUtils()

      ObjectUtils instances should NOT be constructed in standard programming. Instead, the static methods on the class should be used, such as ObjectUtils.defaultIfNull("a","b");.

      This constructor is public to permit tools that require a JavaBean instance to operate.

  • Method Details

    • defaultIfNull

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

      Returns a default value if the object passed is null.

       ObjectUtils.defaultIfNull(null, null)      = null
       ObjectUtils.defaultIfNull(null, "")        = ""
       ObjectUtils.defaultIfNull(null, "zz")      = "zz"
       ObjectUtils.defaultIfNull("abc", *)        = "abc"
       ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE
       
      Type Parameters:
      T - the type of the object
      Parameters:
      object - the Object to test, may be null
      defaultValue - the default value to return, may be null
      Returns:
      object if it is not null, defaultValue otherwise
    • firstNonNull

      @SafeVarargs public static <T> T firstNonNull(T... values)

      Returns the first value in the array which is not null. If all the values are null or the array is null or empty then 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
       
      Type Parameters:
      T - the component type of the array
      Parameters:
      values - the values to test, may be null or empty
      Returns:
      the first value from values which is not null, or null if there are no non-null values
      Since:
      3.0
    • anyNotNull

      public static boolean anyNotNull(Object... values)
      Checks if any value in the given array is not null.

      If all the values are null or the array is null or empty then false is returned. Otherwise true is returned.

       ObjectUtils.anyNotNull(*)                = true
       ObjectUtils.anyNotNull(*, null)          = true
       ObjectUtils.anyNotNull(null, *)          = true
       ObjectUtils.anyNotNull(null, null, *, *) = true
       ObjectUtils.anyNotNull(null)             = false
       ObjectUtils.anyNotNull(null, null)       = false
       
      Parameters:
      values - the values to test, may be null or empty
      Returns:
      true if there is at least one non-null value in the array, false if all values in the array are nulls. If the array is null or empty false is also returned.
      Since:
      3.5
    • allNotNull

      public static boolean allNotNull(Object... values)
      Checks if all values in the array are not nulls.

      If any value is null or the array is null then false is returned. If all elements in array are not null or the array is empty (contains no elements) true is returned.

       ObjectUtils.allNotNull(*)             = true
       ObjectUtils.allNotNull(*, *)          = true
       ObjectUtils.allNotNull(null)          = false
       ObjectUtils.allNotNull(null, null)    = false
       ObjectUtils.allNotNull(null, *)       = false
       ObjectUtils.allNotNull(*, null)       = false
       ObjectUtils.allNotNull(*, *, null, *) = false
       
      Parameters:
      values - the values to test, may be null or empty
      Returns:
      false if there is at least one null value in the array or the array is null, true if all values in the array are not nulls or array contains no elements.
      Since:
      3.5
    • equals

      @Deprecated public static boolean equals(Object object1, Object object2)
      Deprecated.
      this method has been replaced by java.util.Objects.equals(Object, Object) in Java 7 and will be removed from future releases.

      Compares two objects for equality, where either one or both objects may be 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 null
      object2 - the second object, may be null
      Returns:
      true if the values of both objects are the same
    • notEqual

      public static boolean notEqual(Object object1, Object object2)

      Compares two objects for inequality, where either one or both objects may be 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 null
      object2 - the second object, may be null
      Returns:
      false if the values of both objects are the same
    • hashCode

      @Deprecated public static int hashCode(Object obj)
      Deprecated.
      this method has been replaced by java.util.Objects.hashCode(Object) in Java 7 and will be removed in future releases

      Gets the hash code of an object returning zero when the object is null.

       ObjectUtils.hashCode(null)   = 0
       ObjectUtils.hashCode(obj)    = obj.hashCode()
       
      Parameters:
      obj - the object to obtain the hash code of, may be null
      Returns:
      the hash code of the object, or zero if null
      Since:
      2.1
    • hashCodeMulti

      @Deprecated public static int hashCodeMulti(Object... objects)
      Deprecated.
      this method has been replaced by java.util.Objects.hash(Object...) in Java 7 and will be removed in future releases.

      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(Object). The hash code for multiple objects is the same as that calculated by an 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 null
      Returns:
      the hash code of the objects, or zero if null
      Since:
      3.0
    • identityToString

      public static String identityToString(Object object)

      Gets the toString that would be produced by Object if a class did not override toString itself. null will return 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 null
      Returns:
      the default toString text, or null if null passed in
    • identityToString

      public static void identityToString(Appendable appendable, Object object) throws IOException

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

       ObjectUtils.identityToString(appendable, "")            = appendable.append("java.lang.String@1e23"
       ObjectUtils.identityToString(appendable, Boolean.TRUE)  = appendable.append("java.lang.Boolean@7fa"
       ObjectUtils.identityToString(appendable, Boolean.TRUE)  = appendable.append("java.lang.Boolean@7fa")
       
      Parameters:
      appendable - the appendable to append to
      object - the object to create a toString for
      Throws:
      IOException - if an I/O error occurs
      Since:
      3.2
    • identityToString

      @Deprecated public static void identityToString(StrBuilder builder, Object object)
      Deprecated.
      as of 3.6, because StrBuilder was moved to commons-text, use one of the other identityToString methods instead

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

       ObjectUtils.identityToString(builder, "")            = builder.append("java.lang.String@1e23"
       ObjectUtils.identityToString(builder, Boolean.TRUE)  = builder.append("java.lang.Boolean@7fa"
       ObjectUtils.identityToString(builder, Boolean.TRUE)  = builder.append("java.lang.Boolean@7fa")
       
      Parameters:
      builder - the builder to append to
      object - the object to create a toString for
      Since:
      3.2
    • identityToString

      public static void identityToString(StringBuffer buffer, Object object)

      Appends the toString that would be produced by Object if a class did not override toString itself. 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
      Since:
      2.4
    • identityToString

      public static void identityToString(StringBuilder builder, Object object)

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

       ObjectUtils.identityToString(builder, "")            = builder.append("java.lang.String@1e23"
       ObjectUtils.identityToString(builder, Boolean.TRUE)  = builder.append("java.lang.Boolean@7fa"
       ObjectUtils.identityToString(builder, Boolean.TRUE)  = builder.append("java.lang.Boolean@7fa")
       
      Parameters:
      builder - the builder to append to
      object - the object to create a toString for
      Since:
      3.2
    • toString

      @Deprecated public static String toString(Object obj)
      Deprecated.
      this method has been replaced by java.util.Objects.toString(Object) in Java 7 and will be removed in future releases. Note however that said method will return "null" for null references, while this method returns an empty String. To preserve behavior use java.util.Objects.toString(myObject, "")

      Gets the toString of an Object returning an empty string ("") if null input.

       ObjectUtils.toString(null)         = ""
       ObjectUtils.toString("")           = ""
       ObjectUtils.toString("bat")        = "bat"
       ObjectUtils.toString(Boolean.TRUE) = "true"
       
      Parameters:
      obj - the Object to toString, may be null
      Returns:
      the passed in Object's toString, or "" if null input
      Since:
      2.0
      See Also:
    • toString

      @Deprecated public static String toString(Object obj, String nullStr)
      Deprecated.
      this method has been replaced by java.util.Objects.toString(Object, String) in Java 7 and will be removed in future releases.

      Gets the toString of an Object returning a specified text if 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 toString, may be null
      nullStr - the String to return if null input, may be null
      Returns:
      the passed in Object's toString, or nullStr if null input
      Since:
      2.0
      See Also:
    • min

      @SafeVarargs public static <T extends Comparable<? super T>> T min(T... values)

      Null safe comparison of Comparables.

      Type Parameters:
      T - type of the values processed by this method
      Parameters:
      values - the set of comparable values, may be null
      Returns:
      • If any objects are non-null and unequal, the lesser object.
      • If all objects are non-null and equal, the first.
      • If any of the comparables are null, the lesser of the non-null objects.
      • If all the comparables are null, null is returned.
    • max

      @SafeVarargs public static <T extends Comparable<? super T>> T max(T... values)

      Null safe comparison of Comparables.

      Type Parameters:
      T - type of the values processed by this method
      Parameters:
      values - the set of comparable values, may be null
      Returns:
      • If any objects are non-null and unequal, the greater object.
      • If all objects are non-null and equal, the first.
      • If any of the comparables are null, the greater of the non-null objects.
      • If all the comparables are null, null is returned.
    • compare

      public static <T extends Comparable<? super T>> int compare(T c1, T c2)

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

      Type Parameters:
      T - type of the values processed by this method
      Parameters:
      c1 - the first comparable, may be null
      c2 - the second comparable, may be null
      Returns:
      a negative value if c1 < c2, zero if c1 = c2 and a positive value if c1 > c2
    • compare

      public static <T extends Comparable<? super T>> int compare(T c1, T c2, boolean nullGreater)

      Null safe comparison of Comparables.

      Type Parameters:
      T - type of the values processed by this method
      Parameters:
      c1 - the first comparable, may be null
      c2 - the second comparable, may be null
      nullGreater - if true null is considered greater than a non-null value or if false null is considered less than a Non-null value
      Returns:
      a negative value if c1 < c2, zero if c1 = c2 and a positive value if c1 > c2
      See Also:
    • median

      @SafeVarargs public static <T extends Comparable<? super T>> T median(T... items)
      Find the "best guess" middle value among comparables. If there is an even number of total values, the lower of the two middle values will be returned.
      Type Parameters:
      T - type of values processed by this method
      Parameters:
      items - to compare
      Returns:
      T at middle position
      Throws:
      NullPointerException - if items is null
      IllegalArgumentException - if items is empty or contains null values
      Since:
      3.0.1
    • median

      @SafeVarargs public static <T> T median(Comparator<T> comparator, T... items)
      Find the "best guess" middle value among comparables. If there is an even number of total values, the lower of the two middle values will be returned.
      Type Parameters:
      T - type of values processed by this method
      Parameters:
      comparator - to use for comparisons
      items - to compare
      Returns:
      T at middle position
      Throws:
      NullPointerException - if items or comparator is null
      IllegalArgumentException - if items is empty or contains null values
      Since:
      3.0.1
    • mode

      @SafeVarargs public static <T> T mode(T... items)
      Find the most frequently occurring item.
      Type Parameters:
      T - type of values processed by this method
      Parameters:
      items - to check
      Returns:
      most populous T, null if non-unique or no items supplied
      Since:
      3.0.1
    • clone

      public static <T> T clone(T obj)

      Clone an object.

      Type Parameters:
      T - the type of the object
      Parameters:
      obj - the object to clone, null returns null
      Returns:
      the clone if the object implements Cloneable otherwise null
      Throws:
      CloneFailedException - if the object is cloneable and the clone operation fails
      Since:
      3.0
    • cloneIfPossible

      public static <T> T cloneIfPossible(T obj)

      Clone an object if possible.

      This method is similar to clone(Object), but will return the provided instance as the return value instead of null if the instance is not cloneable. This is more convenient if the caller uses different implementations (e.g. of a service) and some of the implementations do not allow concurrent processing or have state. In such cases the implementation can simply provide a proper clone implementation and the caller's code does not have to change.

      Type Parameters:
      T - the type of the object
      Parameters:
      obj - the object to clone, null returns null
      Returns:
      the clone if the object implements Cloneable otherwise the object itself
      Throws:
      CloneFailedException - if the object is cloneable and the clone operation fails
      Since:
      3.0
    • CONST

      public static boolean CONST(boolean v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static boolean MAGIC_FLAG = ObjectUtils.CONST(true);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the boolean value to return
      Returns:
      the boolean v, unchanged
      Since:
      3.2
    • CONST

      public static byte CONST(byte v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static byte MAGIC_BYTE = ObjectUtils.CONST((byte) 127);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the byte value to return
      Returns:
      the byte v, unchanged
      Since:
      3.2
    • CONST_BYTE

      public static byte CONST_BYTE(int v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static byte MAGIC_BYTE = ObjectUtils.CONST_BYTE(127);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the byte literal (as an int) value to return
      Returns:
      the byte v, unchanged
      Throws:
      IllegalArgumentException - if the value passed to v is larger than a byte, that is, smaller than -128 or larger than 127.
      Since:
      3.2
    • CONST

      public static char CONST(char v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static char MAGIC_CHAR = ObjectUtils.CONST('a');
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the char value to return
      Returns:
      the char v, unchanged
      Since:
      3.2
    • CONST

      public static short CONST(short v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static short MAGIC_SHORT = ObjectUtils.CONST((short) 123);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the short value to return
      Returns:
      the short v, unchanged
      Since:
      3.2
    • CONST_SHORT

      public static short CONST_SHORT(int v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static short MAGIC_SHORT = ObjectUtils.CONST_SHORT(127);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the short literal (as an int) value to return
      Returns:
      the byte v, unchanged
      Throws:
      IllegalArgumentException - if the value passed to v is larger than a short, that is, smaller than -32768 or larger than 32767.
      Since:
      3.2
    • CONST

      public static int CONST(int v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static int MAGIC_INT = ObjectUtils.CONST(123);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the int value to return
      Returns:
      the int v, unchanged
      Since:
      3.2
    • CONST

      public static long CONST(long v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static long MAGIC_LONG = ObjectUtils.CONST(123L);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the long value to return
      Returns:
      the long v, unchanged
      Since:
      3.2
    • CONST

      public static float CONST(float v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static float MAGIC_FLOAT = ObjectUtils.CONST(1.0f);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the float value to return
      Returns:
      the float v, unchanged
      Since:
      3.2
    • CONST

      public static double CONST(double v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static double MAGIC_DOUBLE = ObjectUtils.CONST(1.0);
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Parameters:
      v - the double value to return
      Returns:
      the double v, unchanged
      Since:
      3.2
    • CONST

      public static <T> T CONST(T v)
      This method returns the provided value unchanged. This can prevent javac from inlining a constant field, e.g.,
           public final static String MAGIC_STRING = ObjectUtils.CONST("abc");
       
      This way any jars that refer to this field do not have to recompile themselves if the field's value changes at some future date.
      Type Parameters:
      T - the Object type
      Parameters:
      v - the genericized Object value to return (typically a String).
      Returns:
      the genericized Object v, unchanged (typically a String).
      Since:
      3.2