The java.lang package contains the classes that are
most central to the Java language. As you can see from
Figure 25.1,
the class hierarchy is broad rather than deep, which means
that the classes are independent of each other.
Object is the ultimate superclass of all Java
classes and is therefore at the top of all class
hierarchies. Class is a class that describes a Java
class. There is one Class object for each class
that is loaded into Java.
Boolean, Character, Byte,
Short, Integer, Long, Float,
and Double are immutable class wrappers around each
of the primitive Java data types. These classes are useful
when you need to manipulate primitive types as objects.
They also contain useful conversion and utility methods.
String and StringBuffer are objects that
represent strings. String is an immutable type;
StringBuffer may have its string changed in place.
Runtime provides a number of low-level methods
associated with the Java run-time system. System
provides similar low-level system methods. All the
System methods are class methods, and this class may
not be instantiated. Math is a similar class that
supports only class methods--its methods provide
floating-point math support.
The Thread class provides support for multiple
threads of control running within the same Java interpreter.
Process defines a platform-independent interface to
platform-dependent processes running externally to the Java
interpreter.
Throwable is the root class of the exception and
error hierarchy. Throwable objects are used with the
Java throw and catch statements.
java.lang defines quite a few subclasses of
Throwable. Exception and Error are
the superclasses of all exceptions and errors.
Figure 25.2
and
Figure 25.3
show the class hierarchies for these core Java exceptions
and errors.
Signals an attempt to invoke an abstract method.
public class AbstractMethodError extends IncompatibleClassChangeError {
// Public Constructors
public AbstractMethodError();
public AbstractMethodError(String s);
}
Object->Throwable(Serializable)->Error->LinkageError->IncompatibleClassChangeError->AbstractMethodError
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