org.apache.commons.lang3

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

Version:

$Id: ObjectUtils.java 1669786 2015-03-28 15:09:29Z britter $

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ObjectUtils.Null Class used as a null placeholder where null has another meaning.

Field Summary

Fields

Modifier and Type	Field and Description
static ObjectUtils.Null	NULL Singleton used as a null placeholder where null has another meaning.

Constructor Summary

Constructors

Constructor and Description
ObjectUtils() ObjectUtils instances should NOT be constructed in standard programming.

Method Summary

Methods

Modifier and Type	Method and Description
static <T> T	clone(T obj) Clone an object.
static <T> T	cloneIfPossible(T obj) 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 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 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 <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 this method has been replaced by java.util.Objects.equals(Object, Object) in Java 7 and will be removed from future releases.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	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
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	identityToString(Object object) Gets the toString that would be produced by Object if a class did not override toString itself.
static void	identityToString(StrBuilder builder, Object object) Appends the toString that would be produced by Object if a class did not override toString itself.
static void	identityToString(StringBuffer buffer, Object object) Appends the toString that would be produced by Object if a class did not override toString itself.
static void	identityToString(StringBuilder builder, Object object) Appends the toString that would be produced by Object if a class did not override toString itself.
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	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 and empty String. To preserve behavior use java.util.Objects.toString(myObject, "")
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 Detail

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 Detail

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 Detail

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

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

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

public static void identityToString(StrBuilder 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

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 and 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:

StringUtils.defaultString(String), String.valueOf(Object)

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:

StringUtils.defaultString(String,String), String.valueOf(Object)

min

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

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:

Comparator.compare(Object, Object)

median

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

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

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)
                       throws IllegalArgumentException

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)
                         throws IllegalArgumentException

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