先进行源码阅读
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/*
* Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.lang; // Object.java 所在包
/**
* Class { @code Object} is the root of the class hierarchy.
* Every class has { @code Object} as a superclass. All objects,
* including arrays, implement the methods of this class.
* Object 类是所有类的根父类，包括数组对象的class的父类也是Object
*
* @author unascribed
* @see java.lang.Class
* @since JDK1.0
*/
public class Object {
// 注册native 方法，这里没有注释，需要查阅网络资料: 这个是JNI 调用方法声明，
// 底层C++ 可以直接调用Java_java_lang_Object_registerNatives 参考
private static native void registerNatives();
static {
registerNatives();
}
/**
* 获取某个类的Class对象，每个类都被Class类所描述，每个类在JVM中是一个个具体的Class对象。
*
* Returns the runtime class of this { @code Object}. The returned
* { @code Class} object is the object that is locked by { @code
* static synchronized} methods of the represented class.
*
* <p><b>The actual result type is { @code Class<? extends |X|> }
* where { @code |X|} is the erasure of the static type of the
* expression on which { @code getClass} is called.</b> For
* example, no cast is required in this code fragment:</p>
*
* <p>
* { @code Number n = 0; }<br>
* { @code Class<? extends Number> c = n.getClass(); }
* </p>
*
* @return The { @code Class} object that represents the runtime
* class of this object.
* @jls 15.8.2 Class Literals
*/
public final native Class<?> getClass();
/**
* 输出一个数字，可以唯一标识一个运行时对象
* Returns a hash code value for the object. This method is
* supported for the benefit of hash tables such as those provided by
* { @link java.util.HashMap}.
* <p>
* The general contract of { @code hashCode} is:
* <ul>
* <li>Whenever it is invoked on the same object more than once during
* an execution of a Java application, the { @code hashCode} method
* must consistently return the same integer, provided no information
* used in { @code equals} comparisons on the object is modified.
* This integer need not remain consistent from one execution of an
* application to another execution of the same application.
* <li>If two objects are equal according to the { @code equals(Object)}
* method, then calling the { @code hashCode} method on each of
* the two objects must produce the same integer result.
* <li>It is <em>not</em> required that if two objects are unequal
* according to the { @link java.lang.Object#equals(java.lang.Object)}
* method, then calling the { @code hashCode} method on each of the
* two objects must produce distinct integer results. However, the
* programmer should be aware that producing distinct integer results
* for unequal objects may improve the performance of hash tables.
* </ul>
* <p>
* As much as is reasonably practical, the hashCode method defined by
* class { @code Object} does return distinct integers for distinct
* objects. (This is typically implemented by converting the internal
* address of the object into an integer, but this implementation
* technique is not required by the
* Java™ programming language.)
*
* @return a hash code value for this object.
* @see java.lang.Object#equals(java.lang.Object)
* @see java.lang.System#identityHashCode
*/
public native int hashCode();
/**
* 对比两个对象是否相等，默认使用hashcode进行对比
* Indicates whether some other object is "equal to" this one.
* <p>
* The { @code equals} method implements an equivalence relation
* on non-null object references:
* <ul>
* <li>It is <i>reflexive</i>: for any non-null reference value
* { @code x}, { @code x.equals(x)} should return
* { @code true}.
* <li>It is <i>symmetric</i>: for any non-null reference values
* { @code x} and { @code y}, { @code x.equals(y)}
* should return { @code true} if and only if
* { @code y.equals(x)} returns { @code true}.
* <li>It is <i>transitive</i>: for any non-null reference values
* { @code x}, { @code y}, and { @code z}, if
* { @code x.equals(y)} returns { @code true} and
* { @code y.equals(z)} returns { @code true}, then
* { @code x.equals(z)} should return { @code true}.
* <li>It is <i>consistent</i>: for any non-null reference values
* { @code x} and { @code y}, multiple invocations of
* { @code x.equals(y)} consistently return { @code true}
* or consistently return { @code false}, provided no
* information used in { @code equals} comparisons on the
* objects is modified.
* <li>For any non-null reference value { @code x},
* { @code x.equals(null)} should return { @code false}.
* </ul>
* <p>
* The { @code equals} method for class { @code Object} implements
* the most discriminating possible equivalence relation on objects;
* that is, for any non-null reference values { @code x} and
* { @code y}, this method returns { @code true} if and only
* if { @code x} and { @code y} refer to the same object
* ({ @code x == y} has the value { @code true}).
* <p>
* Note that it is generally necessary to override the { @code hashCode}
* method whenever this method is overridden, so as to maintain the
* general contract for the { @code hashCode} method, which states
* that equal objects must have equal hash codes.
*
* @param obj the reference object with which to compare.
* @return { @code true} if this object is the same as the obj
* argument; { @code false} otherwise.
* @see #hashCode()
* @see java.util.HashMap
*/
public boolean equals(Object obj) {
return (this == obj);
}
/**
* 创建一个当前对象的复制对象，复制后的新对象，和原对象是两个无关的对象
* protected 表示只允许子类使用
* Creates and returns a copy of this object. The precise meaning
* of "copy" may depend on the class of the object. The general
* intent is that, for any object { @code x}, the expression:
* <blockquote>
* <pre>
* x.clone() != x</pre></blockquote>
* will be true, and that the expression:
* <blockquote>
* <pre>
* x.clone().getClass() == x.getClass()</pre></blockquote>
* will be { @code true}, but these are not absolute requirements.
* While it is typically the case that:
* <blockquote>
* <pre>
* x.clone().equals(x)</pre></blockquote>
* will be { @code true}, this is not an absolute requirement.
* <p>
* By convention, the returned object should be obtained by calling
* { @code super.clone}. If a class and all of its superclasses (except
* { @code Object}) obey this convention, it will be the case that
* { @code x.clone().getClass() == x.getClass()}.
* <p>
* By convention, the object returned by this method should be independent
* of this object (which is being cloned). To achieve this independence,
* it may be necessary to modify one or more fields of the object returned
* by { @code super.clone} before returning it. Typically, this means
* copying any mutable objects that comprise the internal "deep structure"
* of the object being cloned and replacing the references to these
* objects with references to the copies. If a class contains only
* primitive fields or references to immutable objects, then it is usually
* the case that no fields in the object returned by { @code super.clone}
* need to be modified.
* <p>
* The method { @code clone} for class { @code Object} performs a
* specific cloning operation. First, if the class of this object does
* not implement the interface { @code Cloneable}, then a
* { @code CloneNotSupportedException} is thrown. Note that all arrays
* are considered to implement the interface { @code Cloneable} and that
* the return type of the { @code clone} method of an array type { @code T[]}
* is { @code T[]} where T is any reference or primitive type.
* Otherwise, this method creates a new instance of the class of this
* object and initializes all its fields with exactly the contents of
* the corresponding fields of this object, as if by assignment; the
* contents of the fields are not themselves cloned. Thus, this method
* performs a "shallow copy" of this object, not a "deep copy" operation.
* <p>
* The class { @code Object} does not itself implement the interface
* { @code Cloneable}, so calling the { @code clone} method on an object
* whose class is { @code Object} will result in throwing an
* exception at run time.
*
* @return a clone of this instance.
* @throws CloneNotSupportedException if the object's class does not
* support the { @code Cloneable} interface. Subclasses
* that override the { @code clone} method can also
* throw this exception to indicate that an instance cannot
* be cloned.
* @see java.lang.Cloneable
*/
protected native Object clone() throws CloneNotSupportedException;
/**
* 输出当前对象的 描述，默认描述是hashcode的输出
* Returns a string representation of the object. In general, the
* { @code toString} method returns a string that
* "textually represents" this object. The result should
* be a concise but informative representation that is easy for a
* person to read.
* It is recommended that all subclasses override this method.
* <p>
* The { @code toString} method for class { @code Object}
* returns a string consisting of the name of the class of which the
* object is an instance, the at-sign character `{ @code @}', and
* the unsigned hexadecimal representation of the hash code of the
* object. In other words, this method returns a string equal to the
* value of:
* <blockquote>
* <pre>
* getClass().getName() + '@' + Integer.toHexString(hashCode())
* </pre></blockquote>
*
* @return a string representation of the object.
*/
public String toString() {
return getClass().getName() + "@" + Integer.toHexString(hashCode());
}
/**
* Wakes up a single thread that is waiting on this object's
* 唤醒一个线程，这个线程正在等待这个对象的锁
* monitor. If any threads are waiting on this object, one of them
* 如果有任何线程在等待，那么有一个会被选中并等待
* is chosen to be awakened. The choice is arbitrary 【任意的】 and occurs at
* 这个选择是任意的。
* the discretion of the implementation. A thread waits on an object's
* 一个线程等待一个对象的锁，是因为线程中调用了对象的wait方法
* monitor by calling one of the { @code wait} methods.
* <p>
* The awakened thread will not be able to proceed until the current
* thread relinquishes【交出】 the lock on this object. The awakened thread will
* compete in the usual manner with any other threads that might be
* actively competing to synchronize on this object; for example, the
* awakened thread enjoys no reliable privilege or disadvantage in being
* the next thread to lock this object.
* <p>
* This method should only be called by a thread that is the owner
* of this object's monitor. A thread becomes the owner of the
* object's monitor in one of three ways:
* 这个方法应该只被一个持有对象锁的线程调用，这个线程将会成为对象锁的持有者，下面是三个例子：
* <ul>
* <li>By executing a synchronized instance method of that object. 同步对象方法，锁的是类对象
* <li>By executing the body of a { @code synchronized} statement
* that synchronizes on the object. 同步代码块，锁的是 传入的 对象
* <li>For objects of type { @code Class,} by executing a
* synchronized static method of that class. 同步静态方法，锁的是 类的Class对象
* </ul>
* <p>
* Only one thread at a time can own an object's monitor.
*
* @throws IllegalMonitorStateException if the current thread is not
* the owner of this object's monitor.
* @see java.lang.Object#notifyAll()
* @see java.lang.Object#wait()
*/
public final native void notify();
/**
* Wakes up all threads that are waiting on this object's monitor. A
* thread waits on an object's monitor by calling one of the
* { @code wait} methods.
* notifyAll 方法可以唤醒所有等待这个对象锁的线程。如果这些线程有锁竞争，
* 那么他们获得锁的机会是随机的
* <p>
* The awakened threads will not be able to proceed until the current
* thread relinquishes the lock on this object. The awakened threads
* will compete in the usual manner with any other threads that might
* be actively competing to synchronize on this object; for example,
* the awakened threads enjoy no reliable privilege or disadvantage in
* being the next thread to lock this object.
* <p>
* This method should only be called by a thread that is the owner
* of this object's monitor. See the { @code notify} method for a
* description of the ways in which a thread can become the owner of
* a monitor.
*
* @throws IllegalMonitorStateException if the current thread is not
* the owner of this object's monitor.
* @see java.lang.Object#notify()
* @see java.lang.Object#wait()
*/
public final native void notifyAll();
/**
* 支持超时的wait机制，如果一个线程，执行了wait(100)，那么这个线程将在100ms之后，线程会被唤醒
* Causes the current thread to wait until either another thread invokes the
* { @link java.lang.Object#notify()} method or the
* { @link java.lang.Object#notifyAll()} method for this object, or a
* specified amount of time has elapsed【流逝】.
* <p>
* The current thread must own this object's monitor.
* <p>
* This method causes the current thread (call it <var>T</var>) to
* place itself in the wait set for this object and then to relinquish
* any and all synchronization claims on this object. Thread <var>T</var>
* becomes disabled for thread scheduling purposes and lies dormant
* until one of four things happens:
* <ul>
* <li>Some other thread invokes the { @code notify} method for this
* object and thread <var>T</var> happens to be arbitrarily chosen as
* the thread to be awakened.
* <li>Some other thread invokes the { @code notifyAll} method for this
* object.
* <li>Some other thread { @linkplain Thread#interrupt() interrupts}
* thread <var>T</var>.
* <li>The specified amount of real time has elapsed, more or less. If
* { @code timeout} is zero, however, then real time is not taken into
* consideration and the thread simply waits until notified.
* </ul>
* The thread <var>T</var> is then removed from the wait set for this
* object and re-enabled for thread scheduling. It then competes in the
* usual manner with other threads for the right to synchronize on the
* object; once it has gained control of the object, all its
* synchronization claims on the object are restored to the status quo
* ante - that is, to the situation as of the time that the { @code wait}
* method was invoked. Thread <var>T</var> then returns from the
* invocation of the { @code wait} method. Thus, on return from the
* { @code wait} method, the synchronization state of the object and of
* thread { @code T} is exactly as it was when the { @code wait} method
* was invoked.
* <p>
* A thread can also wake up without being notified, interrupted, or
* timing out, a so-called <i>spurious wakeup</i>. While this will rarely
* occur in practice, applications must guard against it by testing for
* the condition that should have caused the thread to be awakened, and
* continuing to wait if the condition is not satisfied. In other words,
* waits should always occur in loops, like this one:
* <pre>
* synchronized (obj) {
* while (<condition does not hold>)
* obj.wait(timeout);
* ... // Perform action appropriate to condition
* }
* </pre>
* (For more information on this topic, see Section 3.2.3 in Doug Lea's
* "Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
* 2000), or Item 50 in Joshua Bloch's "Effective Java Programming
* Language Guide" (Addison-Wesley, 2001).
*
* <p>If the current thread is { @linkplain java.lang.Thread#interrupt()
* interrupted} by any thread before or while it is waiting, then an
* { @code InterruptedException} is thrown. This exception is not
* thrown until the lock status of this object has been restored as
* described above.
*
* <p>
* Note that the { @code wait} method, as it places the current thread
* into the wait set for this object, unlocks only this object; any
* other objects on which the current thread may be synchronized remain
* locked while the thread waits.
* <p>
* This method should only be called by a thread that is the owner
* of this object's monitor. See the { @code notify} method for a
* description of the ways in which a thread can become the owner of
* a monitor.
*
* @param timeout the maximum time to wait in milliseconds.
* @throws IllegalArgumentException if the value of timeout is
* negative.
* @throws IllegalMonitorStateException if the current thread is not
* the owner of the object's monitor.
* @throws InterruptedException if any thread interrupted the
* current thread before or while the current thread
* was waiting for a notification. The <i>interrupted
* status</i> of the current thread is cleared when
* this exception is thrown.
* @see java.lang.Object#notify()
* @see java.lang.Object#notifyAll()
*/
public final native void wait(long timeout) throws InterruptedException;
/**
* Causes the current thread to wait until another thread invokes the
* { @link java.lang.Object#notify()} method or the
* { @link java.lang.Object#notifyAll()} method for this object, or
* some other thread interrupts the current thread, or a certain
* amount of real time has elapsed.
* <p>
* This method is similar to the { @code wait} method of one
* argument, but it allows finer control over the amount of time to
* wait for a notification before giving up. The amount of real time,
* measured in nanoseconds, is given by:
* <blockquote>
* <pre>
* 1000000*timeout+nanos </pre></blockquote>
* <p>
* In all other respects, this method does the same thing as the
* method { @link #wait(long)} of one argument. In particular,
* { @code wait(0, 0)} means the same thing as { @code wait(0)}.
* <p>
* The current thread must own this object's monitor. The thread
* releases ownership of this monitor and waits until either of the
* following two conditions has occurred:
* <ul>
* <li>Another thread notifies threads waiting on this object's monitor
* to wake up either through a call to the { @code notify} method
* or the { @code notifyAll} method.
* <li>The timeout period, specified by { @code timeout}
* milliseconds plus { @code nanos} nanoseconds arguments, has
* elapsed.
* </ul>
* <p>
* The thread then waits until it can re-obtain ownership of the
* monitor and resumes execution.
* <p>
* As in the one argument version, interrupts and spurious wakeups are
* possible, and this method should always be used in a loop:
* <pre>
* synchronized (obj) {
* while (<condition does not hold>)
* obj.wait(timeout, nanos);
* ... // Perform action appropriate to condition
* }
* </pre>
* This method should only be called by a thread that is the owner
* of this object's monitor. See the { @code notify} method for a
* description of the ways in which a thread can become the owner of
* a monitor.
*
* @param timeout the maximum time to wait in milliseconds.
* @param nanos additional time, in nanoseconds range
* 0-999999.
* @throws IllegalArgumentException if the value of timeout is
* negative or the value of nanos is
* not in the range 0-999999.
* @throws IllegalMonitorStateException if the current thread is not
* the owner of this object's monitor.
* @throws InterruptedException if any thread interrupted the
* current thread before or while the current thread
* was waiting for a notification. The <i>interrupted
* status</i> of the current thread is cleared when
* this exception is thrown.
*/
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 > 0) {
timeout++;
}
wait(timeout);
}
/**
* 一个持有锁的线程，执行wait将被阻塞，知道被notify 或者 notifyAll 唤醒
* Causes the current thread to wait until another thread invokes the
* { @link java.lang.Object#notify()} method or the
* { @link java.lang.Object#notifyAll()} method for this object.
* In other words, this method behaves exactly as if it simply
* performs the call { @code wait(0)}.
* <p>
* The current thread must own this object's monitor. The thread
* releases ownership of this monitor and waits until another thread
* notifies threads waiting on this object's monitor to wake up
* either through a call to the { @code notify} method or the
* { @code notifyAll} method. The thread then waits until it can
* re-obtain ownership of the monitor and resumes execution.
* <p>
* As in the one argument version, interrupts and spurious wakeups are
* possible, and this method should always be used in a loop:
* <pre>
* synchronized (obj) {
* while (<condition does not hold>)
* obj.wait();
* ... // Perform action appropriate to condition
* }
* </pre>
* This method should only be called by a thread that is the owner
* of this object's monitor. See the { @code notify} method for a
* description of the ways in which a thread can become the owner of
* a monitor.
*
* @throws IllegalMonitorStateException if the current thread is not
* the owner of the object's monitor.
* @throws InterruptedException if any thread interrupted the
* current thread before or while the current thread
* was waiting for a notification. The <i>interrupted
* status</i> of the current thread is cleared when
* this exception is thrown.
* @see java.lang.Object#notify()
* @see java.lang.Object#notifyAll()
*/
public final void wait() throws InterruptedException {
wait(0);
}
/**
* 这个是垃圾回收器调用的方法，实现对一个无引用对象进行回收
* Called by the garbage collector on an object when garbage collection
* determines that there are no more references to the object.
* A subclass overrides the { @code finalize} method to dispose of
* system resources or to perform other cleanup.
* <p>
* The general contract of { @code finalize} is that it is invoked
* if and when the Java™ virtual
* machine has determined that there is no longer any
* means by which this object can be accessed by any thread that has
* not yet died, except as a result of an action taken by the
* finalization of some other object or class which is ready to be
* finalized. The { @code finalize} method may take any action, including
* making this object available again to other threads; the usual purpose
* of { @code finalize}, however, is to perform cleanup actions before
* the object is irrevocably discarded. For example, the finalize method
* for an object that represents an input/output connection might perform
* explicit I/O transactions to break the connection before the object is
* permanently discarded.
* <p>
* The { @code finalize} method of class { @code Object} performs no
* special action; it simply returns normally. Subclasses of
* { @code Object} may override this definition.
* <p>
* The Java programming language does not guarantee which thread will
* invoke the { @code finalize} method for any given object. It is
* guaranteed, however, that the thread that invokes finalize will not
* be holding any user-visible synchronization locks when finalize is
* invoked. If an uncaught exception is thrown by the finalize method,
* the exception is ignored and finalization of that object terminates.
* <p>
* After the { @code finalize} method has been invoked for an object, no
* further action is taken until the Java virtual machine has again
* determined that there is no longer any means by which this object can
* be accessed by any thread that has not yet died, including possible
* actions by other objects or classes which are ready to be finalized,
* at which point the object may be discarded.
* <p>
* The { @code finalize} method is never invoked more than once by a Java
* virtual machine for any given object.
* <p>
* Any exception thrown by the { @code finalize} method causes
* the finalization of this object to be halted, but is otherwise
* ignored.
*
* @throws Throwable the { @code Exception} raised by this method
* @see java.lang.ref.WeakReference
* @see java.lang.ref.PhantomReference
* @jls 12.6 Finalization of Class Instances
*/
protected void finalize() throws Throwable { }
}
类-Object 总结：
Object 类是Java中所有类的根父类，这个类大部分都是native方法，也就是说大部分方法都是native底层（如果进一步研究，需要看底层的C++逻辑）实现的。Object类包含以下方法：
- native方法注册方法
private static native void registerNatives();
- 对象操作状态、复制方法
public native int hashCode();
public boolean equals(Object obj) 默认对比的是hashcode
protected native Object clone() throws CloneNotSupportedException;
public String toString()
- 对象锁相关操作方法，涉及
synchronized、多线程能力
public final native void notify(); 唤醒持有对象锁的其他线程
public final native void notifyAll(); 唤醒持有对象锁的所有线程
public final native void wait(long timeout) throws InterruptedException; 当前线程阻塞timeout ms后唤醒
public final void wait(long timeout, int nanos) throws InterruptedException 当前线程阻塞 timeout ms后唤醒
public final void wait() throws InterruptedException 当前线程阻塞 直到被notify、notifyAll唤醒，所多线程通信的示例模版代码：
// 一种写法：按照条件阻塞
while (condition run thread) { // 总循环条件
synchronized (obj) {
while (condition does not hold) { // 需要阻塞的 循环条件
obj.wait(timeout, nanos); // 阻塞等待 timeouts
}
// Perform action appropriate to condition 执行适合条件的动作
.....
obj.notify()// obj.notifyAll()
}
}
// 另一种写法：按照条件执行
while (condition run thread) { // 总循环条件
synchronized (obj) {
if (condition run something) {
// Perform action appropriate to condition 执行适合条件的动作
.....
obj.notify()// obj.notifyAll()
} else {
obj.wait(timeout, nanos); // 阻塞等待 timeouts
}
}
}
- gc相关的方法，实现对对象的回收
protected void finalize() throws Throwable { }
多线程相关面试题
考察wait、notify、notifyAll和线程的搭配使用，实现通信
实现两个线程交替打印奇偶数，保证不错乱
package code.code2024.alibab;
/**
* 题目说明：使用java多线程，实现两个线程交替打印奇偶数，保证不错乱
* 理论基础：synchronized的使用 和 Object class的学习，以及多线程通信的状态变量的定义和操作
*/
public class PrintNumbersInOrder {
static Object o = new Object(); // 线程间的锁
// 线程通信的状态变量
static volatile int count = 0;
public static void main(String[] args) {
Runnable a = new Runnable() {
@Override
public void run() {
// 线程结束循环
while (count < 100) {
synchronized (o) { // 对象锁，代码块
// 满足条件，执行内容，并通知其他线程
if(count % 2 == 0) {
System.out.println("a print count = " + count);
count++; // 完成自己的操作
o.notify(); // 唤醒另一个线程
} else {
// 不满足条件，自己等待
try {
o.wait();
} catch (InterruptedException e) {
System.out.println("InterruptedException = " + e.getMessage());
}
}
}
}
}
};
Runnable b = new Runnable() {
@Override
public void run() {
while (count < 100) {
synchronized (o) {
// 满足条件，执行内容，并通知其他线程
if(count % 2 == 1) {
System.out.println("b print count = " + count);
count++;
o.notify(); // 唤醒另一个线程
} else {
// 不满足条件，等待
try {
o.wait(); // 当前线程等待
} catch (InterruptedException e) {
System.out.println("InterruptedException = " + e.getMessage());
}
}
}
}
}
};
// 启动两个线程
new Thread(a).start();
new Thread(b).start();
}
}
实现A B C线程分别打印 1 2 3，保证不错乱，确保测试程序可以输出123123123
package code.code2024.alibab;
public class MThread {
public static void print(String s) {
System.out.print(s);
}
public static class Test {
public void first() {
print("1");
}
public void second() {
print("2");
}
public void third() {
print("3");
}
}
// 线程实践的锁
static Test t = new Test();
// 线程通信控制变量
static volatile int count = 0;
public static void main(String[] args) {
Thread A = new Thread(new Runnable() {
@Override
public void run() {
synchronized (t) { // 获取对象锁
while (count < 9) { // 循环，设定一个条件退出线程
if (count % 3 == 0) { // 满足目标状态条件，
t.first();// 执行操作
count++;// 状态转移
t.notifyAll(); // 唤起全部其他线程（因为有三个线程，所以要调用notifyAll）
} else { // 不满足条件，当前线程阻塞住
try {
t.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
});
Thread B = new Thread(new Runnable() {
@Override
public void run() {
synchronized (t) {
while (count < 9) {
if (count % 3 == 1) {
t.second();
count++;
t.notifyAll();
} else {
try {
t.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
});
Thread C = new Thread(new Runnable() {
@Override
public void run() {
synchronized (t) {
while (count < 9) {
if (count % 3 == 2) {
t.third();
count++;
t.notifyAll();
} else {
try {
t.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
});
A.start();
B.start();
C.start();
}
}
进一步研究JVM层Object native 方法的 C++代码
涉及：C++、JNI、内核态等
待更新
参考资料
jvm源码下载 github.com/openjdk/jdk
