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 960138 2010-07-03 00:30:46Z joehni $

Author:

Apache Software Foundation, Nissim Karpenstein, Janek Bogucki, Daniel L. Rall, Gary Gregory, Mario Winterer, David J. M. Karlsen

Nested Class Summary

static class

ObjectUtils.Null Class used as a null placeholder where null has another meaning.

Field Summary

static ObjectUtils.Null

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

Constructor Summary

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

Method Summary

static <T> T	clone(T o) Clone an object.
static <T> T	cloneIfPossible(T o) Clone an object if possible.
static Object	defaultIfNull(Object object, Object defaultValue) Returns a default value if the object passed is null.
static boolean	equals(Object object1, Object object2) Compares two objects for equality, where either one or both objects may be null.
static <T> T	firstNonNull(T... values) Returns the first value in the array which is not null.
static int	hashCode(Object obj) Gets the hash code of an object returning zero when the object is null.
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(StringBuffer buffer, 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 c1, T c2) Null safe comparison of Comparables.
static <T extends Comparable<? super T>> T	min(T c1, T c2) Null safe comparison of Comparables.
static String	toString(Object obj) Gets the toString of an Object returning an empty string ("") if null input.
static String	toString(Object obj, String nullStr) Gets the toString of an Object returning a specified text if null input.

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 class should be used as ObjectUtils.defaultIfNull("a","b");.

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

Method Detail

defaultIfNull

public static Object defaultIfNull(Object object,
                                   Object 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
 

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
 

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

equals

public static boolean equals(Object object1,
                             Object object2)

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

hashCode

public static int hashCode(Object obj)

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

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(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

toString

public static String toString(Object obj)

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 nullStr if null input

Since:

2.0

See Also:

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

toString

public static String toString(Object obj,
                              String nullStr)

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 c1,
                                                      T c2)

Null safe comparison of Comparables.

Parameters:

c1 - the first comparable, may be null

c2 - the second comparable, may be null

Returns:

• If both objects are non-null and unequal, the lesser object.
• If both objects are non-null and equal, c1.
• If one of the comparables is null, the non-null object.
• If both the comparables are null, null is returned.

max

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

Null safe comparison of Comparables.

Parameters:

c1 - the first comparable, may be null

c2 - the second comparable, may be null

Returns:

• If both objects are non-null and unequal, the greater object.
• If both objects are non-null and equal, c1.
• If one of the comparables is null, the non-null object.
• If both the comparables are null, null is returned.

clone

public static <T> T clone(T o)

Clone an object.

Type Parameters:

T - the type of the object

Parameters:

o - the object to clone

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 o)

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:

o - the object to clone

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