Package org.apache.commons.lang

Class ObjectUtils

java.lang.Object
org.apache.commons.lang.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 1057434 2011-01-11 01:27:37Z niallp $

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

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

  • Method Details

    • 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

    • 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

    • 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
      Since:
      2.6

    • 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

    • appendIdentityToString

      public static StringBuffer appendIdentityToString(StringBuffer buffer, Object object)
      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

    • 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:

    • 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:

    • min

      public static Object min(Comparable c1, Comparable 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 Object max(Comparable c1, Comparable 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.

    • compare

      public static int compare(Comparable c1, Comparable c2)
      Null safe comparison of Comparables. null is assumed to be less than a non-null value.
      Parameters:
      c1 - the first comparable, may be null
      c2 - the second comparable, may be null
      Returns:
      a negative value if c1 invalid input: '<' c2, zero if c1 = c2 and a positive value if c1 > c2
      Since:
      2.6

    • compare

      public static int compare(Comparable c1, Comparable c2, boolean nullGreater)
      Null safe comparison of Comparables.
      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 invalid input: '<' c2, zero if c1 = c2 and a positive value if c1 > c2
      Since:
      2.6
      See Also:

    • clone

      public static Object clone(Object o)
      Clone an 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:
      2.6

    • cloneIfPossible

      public static Object cloneIfPossible(Object 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.
      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:
      2.6