Java中线程及线程状态是什么意思
本篇内容主要讲解“Java中线程及线程状态是什么意思”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“Java中线程及线程状态是什么意思”吧!
双辽ssl适用于网站、小程序/APP、API接口等需要进行数据传输应用场景，ssl证书未来市场广阔！成为创新互联建站的ssl证书销售渠道，可以享受市场价格4-6折优惠！如果有意向欢迎电话联系或者加微信：028-86922220（备注：SSL证书合作）期待与您的合作！
线程
线程（英语：thread）是操作系统能够进行运算调度的最小单位。它被包含在进程之中，是进程中的实际运作单位。一条线程指的是进程中一个单一顺序的控制流， 一个进程中可以并发多个线程，每条线程并行执行不同的任务。在Unix System V及SunOS中也被称为轻量进程（lightweight processes）， 但轻量进程更多指内核线程（kernel thread），而把用户线程（user thread）称为线程。
以上拷贝自维基百科
代码中任务、逻辑操作都依赖于线程，是java运行时最宝贵的资源
多线程一定程度可以增加cpu使用时间，压榨计算机资源提供更好的使用性能，一定程度也增加了资源的消耗如内存的增长、线程上下文数据切换的消耗、cup资源消耗，实际情况中我们应该根据业务场景合理的使用线程资源
Java线程生命周期
https://www.geeksforgeeks.org/lifecycle-and-states-of-a-thread-in-java/contribute.geeksforgeeks.org/wp-content/uploads/threadLifeCycle.jpg
java.lang.Thread.State 定义了如下6种线程状态
/**
* Thread state for a thread which has not yet started.
*/
NEW,
/**
* Thread state for a runnable thread. A thread in the runnable
* state is executing in the Java virtual machine but it may
* be waiting for other resources from the operating system
* such as processor.
*/
RUNNABLE,
/**
* Thread state for a thread blocked waiting for a monitor lock.
* A thread in the blocked state is waiting for a monitor lock
* to enter a synchronized block/method or
* reenter a synchronized block/method after calling
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
* -
*
- {@link Object#wait() Object.wait} with no timeout *
- {@link #join() Thread.join} with no timeout *
- {@link LockSupport#park() LockSupport.park} *
A thread in the waiting state is waiting for another thread to * perform a particular action. * * For example, a thread that has called Object.wait() * on an object is waiting for another thread to call * Object.notify() or Object.notifyAll() on * that object. A thread that has called Thread.join() * is waiting for a specified thread to terminate. */ WAITING, /** * Thread state for a waiting thread with a specified waiting time. * A thread is in the timed waiting state due to calling one of * the following methods with a specified positive waiting time: *
-
*
- {@link #sleep Thread.sleep} *
- {@link Object#wait(long) Object.wait} with timeout *
- {@link #join(long) Thread.join} with timeout *
- {@link LockSupport#parkNanos LockSupport.parkNanos} *
- {@link LockSupport#parkUntil LockSupport.parkUntil} *
New：刚创建，可被执行，并且未开始执行
Runnable：正在执行或随时准备执行，例如多线程程序分配特定时间片给特定线程，特定线程执行短暂时间并暂停放弃cpu时间给其他线程，其他线程因此可以执行，这种场景线程是准备执行等待CPU时间，这种状态即Runnable
Blocked：waiting for a monitor lock，处于需要获取其他线程锁定的同步资源，如等待io结束，这种状态在转变为Runnable之前无法执行，无法消耗cup时间片
Waiting：等待其他线程执行特定操作，和Blocked类似
Timed Waiting：线程调用等待执行场景，特定时间后执行，比较sleep，或者一些条件等待场景，如定时任务
Terminated：正常或异常结束线程，将不分配CPU时间
模拟线程生命周期
1线程状态转换
public class DemonstrateThreadStates2 {
static Thread thread1;
public static void main(String[] args) {
//创建线程1
thread1 = new Thread(new TestThread1());
// thread1 创建后 NEW state.
System.out.println("State of thread1 after creating it - ">控制台输出：
State of thread1 after creating it - NEW State of thread1 after calling .start() method on it - RUNNABLE State of thread2 after creating it - NEW State of thread2 after calling .start() method on it - RUNNABLE State of thread2 after calling .sleep() method on it - TIMED_WAITING State of thread1 while it called join() method on thread2 -WAITING State of thread2 when it has finished it's execution - TERMINATED
线程创建线程变成NEW状态，调用start启动线程变成Runnable，调用sleep阻塞当前线程吧变成Timed Waiting，thread2调用join将等待结束当前线程到父线程thread1，thread2线程将变成die，父线程thread1 等待线程thread2结束变成waiting
2模拟blocked场景
通过死锁模拟blocked场景
死锁条件
互斥使用：一个资源只能分配给一个线程
不可剥夺：资源只能由占有者释放，申请者不能强制剥夺
请求保持：线程申请资源时，保持对原有资源的占有
循环等待：存在一个进程等待队列：{P1 , P2 , … , Pn}, 其中P1等待P2占有的资源，P2等待P3占有的资源，…，Pn等待P1占有的资源，形成一个进程等待环路
代码public class TestDeadLock implements Runnable {
// flag=1，占有对象o1，等待对象o2
// flag=0，占有对象o2，等待对象o1
public int flag = 1;
// 定义两个Object对象，模拟两个线程占有的资源
public static Object o1 = new Object();
public static Object o2 = new Object();
public static void main(String[] args) {
TestDeadLock deadLock1 = new TestDeadLock();
TestDeadLock deadLock2 = new TestDeadLock();
deadLock1.flag = 0;
deadLock2.flag = 1;
Thread thread1 = new Thread(deadLock1);
Thread thread2 = new Thread(deadLock2);
thread1.start();
thread2.start();
}
@Override
public void run() {
System.out.println("flag: " + flag);
// deadLock2占用资源o1，准备获取资源o2
if (flag == 1) {
synchronized (o1) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (o2) {
System.out.println("1");
}
}
}
// deadLock1占用资源o2，准备获取资源o1
else if (flag == 0) {
synchronized (o2) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (o1) {
System.out.println("0");
}
}
}
}
}参考文献
https://www.geeksforgeeks.org/lifecycle-and-states-of-a-thread-in-java/
https://www.jianshu.com/p/8cf78bf94f9d
到此，相信大家对“Java中线程及线程状态是什么意思”有了更深的了解，不妨来实际操作一番吧！这里是创新互联网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
当前文章：Java中线程及线程状态是什么意思
网站地址：http://cdiso.cn/article/gohohc.html
