java.lang Package

In this tutorial I'll show you the main classes and methods in java.lang package.

Here are the main classes in java.lang package.

• classses
• Boolean
• Byte
• Character
• Character.Subset
• Character.UnicodeBlock
• Class<T>
• ClassLoader
• Compiler
• Double
• Enum<E extends Enum<E>>
• Float
• InheritableThreadLocal<T>
• Integer
• Long
• Math
• Number
• Object
• Package
• Process
• ProcessBuilder
• Runtime
• RuntimePermission
• SecurityManager
• Short
• StackTraceElement
• StrictMath
• String
• StringBuffer
• StringBuilder
• System
• Thread
• ThreadGroup
• ThreadLocal<T>
• Throwable
• Void
• Interfaces
• Appendable
• CharSequence
• Cloneable
• Comparable<T>
• Iteratable<T>
• Readable
• Runnable
• Thread.UncaughtExceptionHandler

First we take a look at the most important class Object class. Object class has several methods. Some methods are very useful. Here are the methods in Object class.

• protected Object clone()
• boolean equals(Object obj)
• protected void finalize()
• Class<?> getClass()
• int hashCode()
• void notify()
• void notifyAll()
• String toString()
• void wait()
• void wait(long timeout)
• void wait(long timeout, int nanos)

Now We take a look at some examples of these methods.

• protected void finalize() throws Throwable
• Called by garbage collector. (System.gc)
• We can override this method to cleanup some resources
• Not invoked more than once by a virtual machine for given object.