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java.lang.Objectorg.apache.commons.lang.ObjectUtils
public class ObjectUtils
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#
| 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 StringBuffer |
appendIdentityToString(StringBuffer buffer,
Object object)
Deprecated. The design of this method is bad - see LANG-360. Instead, use identityToString(StringBuffer, Object). |
static Object |
clone(Object o)
Clone an object. |
static Object |
cloneIfPossible(Object o)
Clone an object if possible. |
static int |
compare(Comparable c1,
Comparable c2)
Null safe comparison of Comparables. |
static int |
compare(Comparable c1,
Comparable c2,
boolean nullGreater)
Null safe comparison of Comparables. |
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 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 Object |
max(Comparable c1,
Comparable c2)
Null safe comparison of Comparables. |
static Object |
min(Comparable c1,
Comparable c2)
Null safe comparison of Comparables. |
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)
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 |
|---|
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 |
|---|
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 |
|---|
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
object - the Object to test, may be nulldefaultValue - the default value to return, may be null
object if it is not null, defaultValue otherwise
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
object1 - the first object, may be nullobject2 - the second object, may be null
true if the values of both objects are the same
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
object1 - the first object, may be nullobject2 - the second object, may be null
false if the values of both objects are the samepublic 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()
obj - the object to obtain the hash code of, may be null
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"
object - the object to create a toString for, may be
null
null if
null passed in
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")
buffer - the buffer to append toobject - the object to create a toString for
public static StringBuffer appendIdentityToString(StringBuffer buffer,
Object object)
Appends the toString that would be produced by Object
if a class did not override toString itself. null
will return null.
ObjectUtils.appendIdentityToString(*, null) = null
ObjectUtils.appendIdentityToString(null, "") = "java.lang.String@1e23"
ObjectUtils.appendIdentityToString(null, Boolean.TRUE) = "java.lang.Boolean@7fa"
ObjectUtils.appendIdentityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa")
buffer - the buffer to append to, may be nullobject - the object to create a toString for, may be null
null if
null passed inpublic 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"
obj - the Object to toString, may be null
null inputStringUtils.defaultString(String),
String.valueOf(Object)
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"
obj - the Object to toString, may be nullnullStr - the String to return if null input, may be null
null inputStringUtils.defaultString(String,String),
String.valueOf(Object)
public static Object min(Comparable c1,
Comparable c2)
c1 - the first comparable, may be nullc2 - the second comparable, may be null
public static Object max(Comparable c1,
Comparable c2)
c1 - the first comparable, may be nullc2 - the second comparable, may be null
public static int compare(Comparable c1,
Comparable c2)
null is assumed to be less than a non-null value.
c1 - the first comparable, may be nullc2 - the second comparable, may be null
public static int compare(Comparable c1,
Comparable c2,
boolean nullGreater)
c1 - the first comparable, may be nullc2 - the second comparable, may be nullnullGreater - if true null is considered greater
than a Non-null value or if false null is
considered less than a Non-null value
Comparator.compare(Object, Object)public static Object clone(Object o)
o - the object to clone
Cloneable otherwise null
CloneFailedException - if the object is cloneable and the clone operation failspublic static Object cloneIfPossible(Object o)
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.
o - the object to clone
Cloneable otherwise the object itself
CloneFailedException - if the object is cloneable and the clone operation fails
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