Class ObjectUtils

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

For example, in a HashMap the java.util.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.

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.

Deprecated: The design of this method is bad - see LANG-360. Instead, use identityToString(StringBuffer, 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")
 

Parameters: buffer the buffer to append to, may be null object the object to create a toString for, may be null

Returns: the default toString text, or null if null passed in

Since: 2.0

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

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

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

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

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

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.

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.

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: defaultString String#valueOf(Object)

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: defaultString String#valueOf(Object)