public class ObjectThe root class of the Java class hierarchy. All non-primitive types (including arrays) inherit either directly or indirectly from this class.
Objectprovides some fundamental methods for accessing the
Classof an object, getting its
hashCode(), or checking whether one object
toString()method can be used to convert an object reference into a printable string and is often overridden in subclasses.
#notify()methods provide a foundation for synchronization, acquiring and releasing an internal monitor associated with each
Constructors Constructor and Description
Object()Constructs a new instance of
Methods Modifier and Type Method and Description
equals(Object o)Compares this instance with the specified object and indicates if they are equal.
Class<? extends Object>
getClass()Returns the unique instance of
Classwhich represents this object's class.
hashCode()Returns an integer hash code for this object.
toString()Returns a string containing a concise, human-readable description of this object.
public boolean equals(Object o)Compares this instance with the specified object and indicates if they are equal. In order to be equal,
omust represent the same object as this instance using a class-specific comparison. The general contract is that this comparison should be both transitive and reflexive.
The implementation in
ois the exact same object as the receiver (using the == operator for comparison). Subclasses often implement
equals(Object)so that it takes into account the two object's types and states.
The general contract for the
hashCode()methods is that if
truefor any two objects, then
hashCode()must return the same value for these objects. This means that subclasses of
Objectusually override either both methods or none of them.
o- the object to compare this instance with.
trueif the specified object is equal to this
- See Also:
getClassReturns the unique instance of
Classwhich represents this object's class. Note that
getClass()is a special case in that it actually returns
Class<? extends Foo>where
Foois the erasure of the type of expression
getClass()was called upon.
As an example, the following code actually compiles, although one might think it shouldn't:
l = new ArrayList (); Class extends List> c = l.getClass();
- this object's
public int hashCode()Returns an integer hash code for this object. By contract, any two objects for which
truemust return the same hash code value. This means that subclasses of
Objectusually override both methods or neither method.
- this object's hash code.
- See Also:
public String toString()Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation simply concatenates the class name, the '@' sign and a hexadecimal representation of the object's
hashCode(), that is, it is equivalent to the following expression:
getClass().getName() + '@' + Integer.toHexString(hashCode())
- a printable representation of this object.