深入理解Thread构造函数

 public Thread(ThreadGroup group, Runnable target) {
        init(group, target, "Thread-" + nextThreadNum(), 0);
    }

    /**
     * Allocates a new {@code Thread} object. This constructor has the same
     * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
     * {@code (null, null, name)}.
     *
     * @param   name
     *          the name of the new thread
     */
    public Thread(String name) {
        init(null, null, name, 0);
    }

    /**
     * Allocates a new {@code Thread} object. This constructor has the same
     * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
     * {@code (group, null, name)}.
     *
     * @param  group
     *         the thread group. If {@code null} and there is a security
     *         manager, the group is determined by {@linkplain
     *         SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
     *         If there is not a security manager or {@code
     *         SecurityManager.getThreadGroup()} returns {@code null}, the group
     *         is set to the current thread's thread group.
     *
     * @param  name
     *         the name of the new thread
     *
     * @throws  SecurityException
     *          if the current thread cannot create a thread in the specified
     *          thread group
     */
    public Thread(ThreadGroup group, String name) {
        init(group, null, name, 0);
    }

import java.util.stream.IntStream;

public class Test {
    public static void main(String[] args) {
        IntStream.range(0,5).boxed()
        .map(
                i->new Thread(
                        ()->System.out.println(
                                Thread.currentThread().getName()
                                )
                        )
                ).forEach(Thread::start);
    }
}

Thread(Runnable target,String name);
Thread(String name);
Thread(ThreadGroup group,Runnable target,String name);
Thread(ThreadGroup group,Runnable target,String name,long stackSize);
Thread(ThreadGroup group,String name);

import java.util.stream.IntStream;


public class Test2 {
    private final static String PREFIX="ALEX-";
    public static void main(String[] args) {
        IntStream.range(0,5).mapToObj(Test2::createTHREAD).forEach(Thread::start);
    }
    private static Thread createTHREAD(final int intName) {
        return new Thread(()->System.out.println(Thread.currentThread().getName()),PREFIX+intName);
    }
}

public final synchronized void setName(String name) {
        checkAccess();
        if (name == null) {
            throw new NullPointerException("name cannot be null");
        }

        this.name = name;
        if (threadStatus != 0) {
            setNativeName(name);
        }
    }

 private void init(ThreadGroup g, Runnable target, String name,
                      long stackSize, AccessControlContext acc,
                      boolean inheritThreadLocals) {
        if (name == null) {
            throw new NullPointerException("name cannot be null");
        }

        this.name = name;

        Thread parent = currentThread();//在这里获取当前线程作为父线程
        SecurityManager security = System.getSecurityManager();
        if (g == null) {
            /* Determine if it's an applet or not */

            /* If there is a security manager, ask the security manager
               what to do. */
            if (security != null) {
                g = security.getThreadGroup();
            }

            /* If the security doesn't have a strong opinion of the matter
               use the parent thread group. */
            if (g == null) {
                g = parent.getThreadGroup();
            }
        }

        /* checkAccess regardless of whether or not threadgroup is
           explicitly passed in. */
        g.checkAccess();

        /*
         * Do we have the required permissions?
         */
        if (security != null) {
            if (isCCLOverridden(getClass())) {
                security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
            }
        }

        g.addUnstarted();

        this.group = g;
        this.daemon = parent.isDaemon();
        this.priority = parent.getPriority();
        if (security == null || isCCLOverridden(parent.getClass()))
            this.contextClassLoader = parent.getContextClassLoader();
        else
            this.contextClassLoader = parent.contextClassLoader;
        this.inheritedAccessControlContext =
                acc != null ? acc : AccessController.getContext();
        this.target = target;
        setPriority(priority);
        if (inheritThreadLocals && parent.inheritableThreadLocals != null)
            this.inheritableThreadLocals =
                ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
        /* Stash the specified stack size in case the VM cares */
        this.stackSize = stackSize;

        /* Set thread ID */
        tid = nextThreadID();
    }

 SecurityManager security = System.getSecurityManager();
        if (g == null) {
            /* Determine if it's an applet or not */

            /* If there is a security manager, ask the security manager
               what to do. */
            if (security != null) {
                g = security.getThreadGroup();
            }

            /* If the security doesn't have a strong opinion of the matter
               use the parent thread group. */
            if (g == null) {
                g = parent.getThreadGroup();
            }
        }

package concurrent.chapter02;

public class ThreadConstruction {
    public static void main(String[] args) {
        Thread t1 = new Thread("t1");
        ThreadGroup group = new ThreadGroup("TestGroup");
        Thread t2 = new Thread(group,"t2");
        ThreadGroup mainThreadGroup = Thread.currentThread().getThreadGroup();
        System.out.println("Main thread belong group:"+mainThreadGroup.getName());
        System.out.println("t1 and main belong the same group:"+(mainThreadGroup==t1.getThreadGroup()));
        System.out.println("t2 thread group not belong main group:"+(mainThreadGroup==t2.getThreadGroup()));
        System.out.println("t2 thread group belong main TestGroup:"+(group==t2.getThreadGroup()));
    }
}

public class DaemonThread {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(()-> {
            while(true) {
                try {
                    Thread.sleep(1);
                }catch(Exception e) {
                    e.printStackTrace();
                }
            }
        });
        thread.start();
        Thread.sleep(2_000L);
        System.out.println("Main thread finished lifestyle");
    }
}

package concurrent.chapter02;

public class DaemonThread {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(()-> {
            while(true) {
                try {
                    Thread.sleep(1);
                }catch(Exception e) {
                    e.printStackTrace();
                }
            }
        });
        thread.setDaemon(true);
        thread.start();
        Thread.sleep(2_000L);
        System.out.println("Main thread finished lifestyle");
    }
}