Chapter 12. The java.lang Package

AbstractMethodError	Java 1.0
java.lang	serializable error PJ1.1

Signals an attempt to invoke an abstract method.

Hierarchy: Object-->Throwable(Serializable)-->Error-->LinkageError-->IncompatibleClassChangeError-->AbstractMethodError

ArithmeticException	Java 1.0
java.lang	serializable unchecked PJ1.1

A RuntimeException that signals an exceptional arithmetic condition, such as integer division by zero.

Hierarchy: Object-->Throwable(Serializable)-->Exception-->RuntimeException-->ArithmeticException

ArrayIndexOutOfBoundsException	Java 1.0
java.lang	serializable unchecked PJ1.1

Signals that an array index less than zero or greater than or equal to the array size has been used.

Hierarchy: Object-->Throwable(Serializable)-->Exception-->RuntimeException-->IndexOutOfBoundsException-->ArrayIndexOutOfBoundsException

Thrown By: Too many methods to list.

ArrayStoreException	Java 1.0
java.lang	serializable unchecked PJ1.1

Signals an attempt to store the wrong type of object into an array.

Hierarchy: Object-->Throwable(Serializable)-->Exception-->RuntimeException-->ArrayStoreException

Boolean	Java 1.0
java.lang	serializable PJ1.1

This class provides an immutable object wrapper around the boolean primitive type. Note that the TRUE and FALSE constants are Boolean objects; they are not the same as the true and falseboolean values. As of Java 1.1, this class defines a Class constant that represents the boolean type. booleanValue() returns the boolean value of a Boolean object. The class method getBoolean() retrieves the boolean value of a named property from the system property list. The class method valueOf() parses a string and returns the boolean value it represents.

Hierarchy: Object-->Boolean(Serializable)

Passed To: javax.swing.DefaultDesktopManager.setWasIcon()

Returned By: Boolean.valueOf(), javax.swing.filechooser.FileView.isTraversable()

Type Of: java.awt.font.TextAttribute.{RUN_DIRECTION_LTR, RUN_DIRECTION_RTL, STRIKETHROUGH_ON, SWAP_COLORS_ON}, Boolean.{FALSE, TRUE}

Byte	Java 1.1
java.lang	serializable comparable PJ1.1

This class provides an object wrapper around the byte primitive type. It defines useful constants for the minimum and maximum values that can be stored by the byte type and a Class object constant that represents the byte type. It also provides various methods for converting Byte values to and from strings and other numeric types.

Most of the static methods of this class can convert a String to a Byte object or a byte value: the four parseByte() and valueOf() methods parse a number from the specified string using an optionally specified radix and return it in one of these two forms. The decode() method parses a byte specified in base 10, base 8, or base 16 and returns it as a Byte. If the string begins with "0x" or "#", it is interpreted as a hexadecimal number. If it begins with "0", it is interpreted as an octal number. Otherwise, it is interpreted as a decimal number.

Note that this class has two toString() methods. One is static and converts a byte primitive value to a string; the other is the usual toString() method that converts a Byte object to a string. Most of the remaining methods convert a Byte to various primitive numeric types.

Hierarchy: Object-->Number(Serializable)-->Byte(Comparable)

Passed To: Byte.compareTo()

Returned By: Byte.{decode(), valueOf()}

Character	Java 1.0
java.lang	serializable comparable PJ1.1

This class provides an immutable object wrapper around the primitive char data type. charValue() returns the char value of a Character object. A number of class methods provide the Java/Unicode equivalent of the C <ctype.h> character macros for checking the type of characters and converting to uppercase and lowercase letters. getType() returns the character type. The return value is one of the constants defined by the class, which represents a number of broad Unicode character categories. digit() returns the integer equivalent of a given character for a given radix (e.g., radix 16 for hexadecimal). forDigit() returns the character that corresponds to the specified value for the specified radix.

Hierarchy: Object-->Character(Comparable,Serializable)

Passed To: Character.compareTo()

Character.Subset	Java 1.2
java.lang

This class represents a named subset of the Unicode character set. The toString() method returns the name of the subset. This is a base class intended for further subclassing. Note, in particular, that it does not provide a way to list the members of the subset, nor a way to test for membership in the subset. See Character.UnicodeBlock.

Subclasses: java.awt.im.InputSubset, Character.UnicodeBlock

Passed To: java.awt.im.InputContext.setCharacterSubsets(), java.awt.im.spi.InputMethod.setCharacterSubsets()

Character.UnicodeBlock	Java 1.2
java.lang

This subclass of Character.Subset defines a number of constants that represent named subsets of the Unicode character set. The subsets and their names are the "character blocks" defined by the Unicode 2.0 specification (see http://www.unicode.org/ ). The static method of() takes a character and returns the Character.UnicodeBlock to which it belongs, or null if it is not part of any defined block. When presented with an unknown Unicode character, this method provides a useful way to determine what alphabet it belongs to.

Returned By: Character.UnicodeBlock.of()

Type Of: Too many fields to list.

Class	Java 1.0
java.lang	serializable PJ1.1

This class represents a Java class or interface, or, as of Java 1.1, any Java type. There is one Class object for each class that is loaded into the Java Virtual Machine, and, as of Java 1.1, there are special Class objects that represent the Java primitive types. The TYPE constants defined by Boolean, Integer, and the other primitive wrapper classes hold these special Class objects. Array types are also represented by Class objects in Java 1.1.

There is no constructor for this class. You can obtain a Class object by calling the getClass() method of any instance of the desired class. In Java 1.1 and later, you can also refer to a Class object by appending .class to the name of a class. Finally, and most interestingly, a class can be dynamically loaded by passing its fully qualified name (i.e., package name plus class name) to the static Class.forName() method. This method loads the named class (if it is not already loaded) into the Java interpreter and returns a Class object for it. Classes can also be loaded with a ClassLoader object.

The newInstance() method creates an instance of a given class; this allows you to create instances of dynamically loaded classes for which you cannot use the new keyword. Note that this method only works when the target class has a no-argument constructor. See newInstance() in java.lang.reflect.Constructor for a more powerful way to instantiate dynamically loaded classes.

getName() returns the name of the class. getSuperclass() returns its superclass. isInterface() tests whether the Class object represents an interface, and getInterfaces() returns an array of the interfaces that this class implements. In Java 1.2 and later, getPackage() returns a Package object that represents the package containing the class. getProtectionDomain() returns the java.security.ProtectionDomain to which this class belongs. The various other get() and is() methods return other information about the represented class; they form part of the Java Reflection API, along with the classes in java.lang.reflect.

Hierarchy: Object-->Class(Serializable)

Passed To: Too many methods to list.

Returned By: Too many methods to list.

Type Of: java.beans.beancontext.BeanContextServiceAvailableEvent.serviceClass, java.beans.beancontext.BeanContextServiceRevokedEvent.serviceClass, Boolean.TYPE, Byte.TYPE, Character.TYPE, Double.TYPE, Float.TYPE, Integer.TYPE, Long.TYPE, Short.TYPE, Void.TYPE

ClassCastException	Java 1.0
java.lang	serializable unchecked PJ1.1

Signals an invalid cast of an object to a type of which it is not an instance.

Hierarchy: Object-->Throwable(Serializable)-->Exception-->RuntimeException-->ClassCastException

ClassCircularityError	Java 1.0
java.lang	serializable error PJ1.1

Signals that a circular dependency has been detected while performing initialization for a class.

Hierarchy: Object-->Throwable(Serializable)-->Error-->LinkageError-->ClassCircularityError

ClassFormatError	Java 1.0
java.lang	serializable error PJ1.1

Signals an error in the binary format of a class file.

Hierarchy: Object-->Throwable(Serializable)-->Error-->LinkageError-->ClassFormatError

Subclasses: UnsupportedClassVersionError

Thrown By: ClassLoader.defineClass()

ClassLoader	Java 1.0
java.lang	PJ1.1

This class is the abstract superclass of objects that know how to load Java classes into a Java VM. Given a ClassLoader object, you can dynamically load a class by calling the public loadClass() method, specifying the full name of the desired class. You can obtain a resource associated with a class by calling getResource(), getResources(), and getResourceAsStream(). Many applications do not need to use ClassLoader directly; these applications use the Class.forName() and Class.getResource() methods to dynamically load classes and resources using the ClassLoader object that loaded the application itself.

In order to load classes over the network or from any source other than the standard system classes, you must use a custom ClassLoader object that knows how to obtain data from that source. A java.net.URLClassLoader is suitable for this purpose for almost all applications. Only rarely should an application need to define a ClassLoader subclass of its own. When this is necessary, the subclass should typically extend java.security.SecureClassLoader and override the findClass() method. This method must find the bytes that comprise the named class, then pass them to the defineClass() method and return the resulting Class object. In Java 1.2 and later, the findClass() method must also define the Package object associated with the class, if it has not already been defined. It can use getPackage() and definePackage() for this purpose. Custom subclasses of ClassLoader should also override findResource() and findResources() to enable the public getResource() and getResources() methods.

Subclasses: java.security.SecureClassLoader

Passed To: Too many methods to list.

Returned By: Class.getClassLoader(), ClassLoader.{getParent(), getSystemClassLoader()}, SecurityManager.currentClassLoader(), Thread.getContextClassLoader(), java.rmi.server.RMIClassLoader.getClassLoader()

ClassNotFoundException	Java 1.0
java.lang	serializable checked PJ1.1

Signals that a class to be loaded cannot be found.

Hierarchy: Object-->Throwable(Serializable)-->Exception-->ClassNotFoundException

Thrown By: Too many methods to list.

Cloneable	Java 1.0
java.lang	cloneable PJ1.1

This interface defines no methods or variables, but indicates that the class that implements it may be cloned (i.e., copied) by calling the Object method clone(). Calling clone() for an object that does not implement this interface (and does not override clone() with its own implementation) causes a CloneNotSupportedException to be thrown.

Implementations: Too many classes to list.

CloneNotSupportedException	Java 1.0
java.lang	serializable checked PJ1.1

Signals that the clone() method has been called for an object of a class that does not implement the Cloneable interface.

Hierarchy: Object-->Throwable(Serializable)-->Exception-->CloneNotSupportedException

Subclasses: java.rmi.server.ServerCloneException

Thrown By: java.awt.datatransfer.DataFlavor.clone(), Object.clone(), java.rmi.server.UnicastRemoteObject.clone(), java.security.MessageDigest.clone(), java.security.MessageDigestSpi.clone(), java.security.Signature.clone(), java.security.SignatureSpi.clone(), javax.crypto.Mac.clone(), javax.crypto.MacSpi.clone(), javax.swing.AbstractAction.clone(), javax.swing.DefaultListSelectionModel.clone(), javax.swing.tree.DefaultTreeSelectionModel.clone()

Comparable	Java 1.2
java.lang	comparable

This interface defines a single method, compareTo(), that is responsible for comparing one object to another and determining their relative order, according to some natural ordering for that class of objects. Any general-purpose class that represents a value that can be sorted or ordered should implement this interface. Any class that does implement this interface can make use of various powerful methods such as java.util.Collections.sort() and java.util.Arrays.binarySearch(). As of Java 1.2, many of the key classes in the Java API have been modified to implement this interface.

The compareTo() object compares this object to the object passed as an argument. It should assume that the supplied object is of the appropriate type; if it is not, it should throw a ClassCastException. If this object is less than the supplied object or should appear before the supplied object in a sorted list, compareTo() should return a negative number. If this object is greater than the supplied object or should come after the supplied object in a sorted list, compareTo() should return a positive integer. If the two objects are equivalent, and their relative order in a sorted list does not matter, compareTo() should return 0. If compareTo() returns 0 for two objects, the equals() method should typically return true. If this is not the case, the Comparable objects are not suitable for use in java.util.TreeSet and java.util.TreeMap classes.

See java.util.Comparator for a way to define an ordering for objects that do not implement Comparable or to define an ordering other than the natural ordering defined by a Comparable class.

Implementations: java.io.File, java.io.ObjectStreamField, Byte, Character, Double, Float, Integer, Long, Short, String, java.math.BigDecimal, java.math.BigInteger, java.text.CollationKey, java.util.Date

Compiler	Java 1.0
java.lang	PJ1.1

The static methods of this class provide an interface to the just-in-time (JIT) byte-code-to-native code compiler in use by the Java interpreter. If no JIT compiler is in use by the VM, these methods do nothing. compileClass() asks the JIT compiler to compile the specified class. compileClasses() asks the JIT compiler to compile all classes that match the specified name. These methods return true if the compilation was successful, or false if it failed or if there is no JIT compiler on the system. enable() and disable() turn just-in-time compilation on and off. command() asks the JIT compiler to perform some compiler-specific operation; this is a hook for vendor extensions. No standard operations have been defined.

Double	Java 1.0
java.lang	serializable comparable PJ1.1

This class provides an immutable object wrapper around the double primitive data type. valueOf() converts a string to a Double, doubleValue() returns the primitive double value of a Double object, and there are other methods for returning a Double value as a variety of other primitive types. This class also provides some useful constants and static methods for testing double values. MIN_VALUE and MAX_VALUE are the smallest (closest to zero) and largest representable double values. isInfinite() in class and instance method forms tests whether a double or a Double has an infinite value. Similarly, isNaN() tests whether a double or Double is not-a-number; this is a comparison that cannot be done directly because the NaN constant never tests equal to any other value, including itself. doubleToLongBits() and longBitsToDouble() allow you to manipulate the bit representation of a double directly.

Hierarchy: Object-->Number(Serializable)-->Double(Comparable)

Passed To: Double.compareTo()

Returned By: Double.valueOf()

Error	Java 1.0
java.lang	serializable error PJ1.1

This class forms the root of the error hierarchy in Java. Subclasses of Error, unlike subclasses of Exception, should not be caught and generally cause termination of the program. Subclasses of Error need not be declared in the throws clause of a method definition. getMessage() returns a message associated with the error. See Throwable for other methods.

Hierarchy: Object-->Throwable(Serializable)-->Error

Subclasses: java.awt.AWTError, LinkageError, ThreadDeath, VirtualMachineError

Passed To: java.rmi.ServerError.ServerError()

Exception	Java 1.0
java.lang	serializable checked PJ1.1

This class forms the root of the exception hierarchy in Java. An Exception signals an abnormal condition that must be specially handled to prevent program termination. Exceptions may be caught and handled. An exception that is not a subclass of RuntimeException must be declared in the throws clause of any method that can throw it. getMessage() returns a message associated with the exception. See Throwable for other methods.

Hierarchy: Object-->Throwable(Serializable)-->Exception

Subclasses: Too many classes to list.

Passed To: Too many methods to list.

Returned By: java.awt.event.InvocationEvent.getException(), java.security.PrivilegedActionException.getException(), javax.ejb.EJBException.getCausedByException(), javax.jms.JMSException.getLinkedException(), org.omg.CORBA.Environment.exception()

Thrown By: java.rmi.server.RemoteCall.executeCall(), java.rmi.server.RemoteRef.invoke(), java.rmi.server.Skeleton.dispatch(), java.security.PrivilegedExceptionAction.run(), javax.naming.spi.NamingManager.getObjectInstance(), javax.naming.spi.ObjectFactory.getObjectInstance()

Type Of: java.io.WriteAbortedException.detail, java.rmi.server.ServerCloneException.detail

ExceptionInInitializerError	Java 1.1
java.lang	serializable error PJ1.1

This error is thrown by the Java Virtual Machine when an exception occurs in the static initializer of a class. You can use the getException() method to obtain the Throwable object that was thrown from the initializer.

Hierarchy: Object-->Throwable(Serializable)-->Error-->LinkageError-->ExceptionInInitializerError

Float	Java 1.0
java.lang	serializable comparable PJ1.1

This class provides an immutable object wrapper around the float primitive data type. valueOf() converts a string to a Float, floatValue() returns the primitive float value of a Float object, and there are methods for returning a Float value as a variety of other primitive types. This class also provides some useful constants and static methods for testing float values. MIN_VALUE and MAX_VALUE are the smallest (closest to zero) and largest representable double values. isInfinite() in class and instance method forms tests whether a float or a Float has an infinite value. Similarly, isNaN() tests whether a float or Float is not-a-number; this is a comparison that cannot be done directly because the NaN constant never tests equal to any other value, including itself. floatToIntBits() and intBitsToFloat() allow you to manipulate the bit representation of a float directly.

Hierarchy: Object-->Number(Serializable)-->Float(Comparable)

Passed To: Float.compareTo()

Returned By: Float.valueOf()

Type Of: Too many fields to list.

IllegalAccessError	Java 1.0
java.lang	serializable error PJ1.1

Signals an attempted use of a class, method, or field that is not accessible.

Hierarchy: Object-->Throwable(Serializable)-->Error-->LinkageError-->IncompatibleClassChangeError-->IllegalAccessError

IllegalAccessException	Java 1.0
java.lang	serializable checked PJ1.1

Signals that a class or initializer is not accessible. Thrown by Class.newInstance().