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This article mainly explains "what are the public methods and functions in Object". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what are the public methods and functions in Object"?

Look directly at the source code of the Object class:

Package java.lang

Public class Object {

Private static native void registerNatives ()

Static {

RegisterNatives ()

}

Public final native Class getClass ()

Public native int hashCode ()

Public boolean equals (Object obj) {

Return (this = = obj)

}

Protected native Object clone () throws CloneNotSupportedException

Public String toString () {

Return getClass () .getName () + "@" + Integer.toHexString (hashCode ())

}

Public final native void notify ()

Public final native void notifyAll ()

Public final native void wait (long timeout) throws InterruptedException

Public final void wait (long timeout, int nanos) throws InterruptedException {

If (timeout

< 0) { throw new IllegalArgumentException("timeout value is negative"); } if (nanos < 0 || nanos >

999999) {

Throw new IllegalArgumentException (

"nanosecond timeout value out of range")

}

If (nanos > = 500000 | | (nanos! = 0 & & timeout = = 0) {

Timeout++

}

Wait (timeout)

}

Public final void wait () throws InterruptedException {

Wait (0)

}

Protected void finalize () throws Throwable {}

}

In fact, look at JDK documents you can know the meaning of these methods, but I will introduce their own understanding of them, which public methods, I will focus on the more difficult to master wait and notify methods.

The specific methods are described as follows:

Public String toString ()

This defaults to the getClass () .getName () +'@'+ Integer.toHexString (hashCode ()) of the printed object.

The class name is @ hash code, but subclasses can override the method to define its own object string, which is most commonly used.

Public final native Class getClass ()

Gets the class name of the object, which can be used in reflection.

Public int hashCode ()

Public boolean equals (Object obj)

The use of these two methods in the Set collection class of the collection framework is very important, because the elements in the Set collection are not allowed to repeat, and how various custom objects determine whether they are duplicated is accomplished by overriding these two methods.

Public final native void notify ()

Public final native void notifyAll ()

Public final void wait ()

Public final native void wait (long timeout)

Public final void wait (long timeout, int nanos)

There are several overloaded methods here, but the core methods are wait method and notify method. If you haven't learned java multithreaded programming, you probably won't come into contact with these two methods, which involves thread synchronization and thread communication under synchronous conditions.

Java thread synchronization mechanism is to ensure that multiple threads access the same shared object without conflict is to lock, operate, release the lock. And this lock is implied in the java object. The lock is also called "synchronization monitor". It is owned by all objects, and you don't have to turn a blind eye.

In fact, it is defined in the Object class, but we do not need to know its existence. In order to prevent the same shared object from conflicts, java uses synchronized to protect the shared object from competition. It can be done by using synchronization methods or synchronous blocks, but what happens when two threads need to communicate in a synchronous environment? If there is no communication mechanism, it is inefficient that two threads can only poll for lock acquisition. Here, the wait and notify methods of the Object class can solve this problem.

The principle of using wait () / notify () to realize communication between threads under the condition of synchronization is as follows:

Use premise: must be a synchronization condition, otherwise the call will be abnormal.

Call wait ()

The calling thread abandons the CPU

The calling thread releases the lock

The calling thread enters the waiting set (pool) of the lock and waits for CPU rescheduling.

Call notify ()

A thread leaves the waiting set of the lock and enters the ready running state.

The notified thread must re-request the lock to execute.

Notify () cannot specify exactly the thread to be notified.

NotifyAll () notifies all threads waiting for the assembly to leave and get ready to run

The following is a classic producer and consumer problem to understand the producer thread Producer and consumer thread Consumer, synchronize a shared object Shop, and use the wait and notify methods to communicate with the code:

Puducer.java producer thread definition

Public class Producer implements Runnable {

Shop shop

Public Producer (Shop shop) {

/ / TODO Auto-generated constructor stub

This.shop=shop

New Thread (this, "producer thread"). Start ()

}

@ Override

Public void run () {

/ / TODO Auto-generated method stub

Int iTunes 0

While (true) {

Shop.put (iTunes +)

}

}

}

Consumer.java consumer thread definition

Public class Consumer implements Runnable {

Shop shop

Public Consumer (Shop shop) {

/ / TODO Auto-generated constructor stub

This.shop=shop

New Thread (this, Consumer Thread). Start ()

}

@ Override

Public void run () {

/ / TODO Auto-generated method stub

While (true) {

Shop.get ()

}

}

}

Shared object Shop.java definition

Public class Shop {

Int no

Boolean hasData=false; / / false means no data true has data

Synchronized int get () {/ / Consumer products

If (hasData==false) {

Try {

Wait (); / / Consumer thread pauses

} catch (InterruptedException e) {

/ / TODO Auto-generated catch block

E.printStackTrace ()

}

}

System.out.println ("consumption:" + no)

The consumption of hasData=false;// is over. Notify production

Notify ()

Return no

}

Synchronized void put (int no) {/ / release products

If (hasData==true) {

Try {

Wait ()

} catch (InterruptedException e) {

/ / TODO Auto-generated catch block

E.printStackTrace ()

}

}

System.out.println ("production:" + no)

HasData=true

This.no=no

Notify ()

}

}

Test class PC.java

Public class PC {

Public static void main (String [] args) {

Shop shop=new Shop ()

New Producer (shop)

New Consumer (shop)

}

}

At this point, I believe you have a deeper understanding of "what are the public methods and functions in Object?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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