1.多线程的两种实现--class A extends Thread,class B implements Runnable---对应的两种启动方法分别是A a = new A();a.start();---B b = new B();new Tread(b).start();

两种方法都要实现public void run() {};

2.几个函数，

long getId ()
返回该线程的标识符。
String getName ()
返回该线程的名称。
int getPriority ()
返回线程的优先级。
3.线程安全

使用关键字synchronized，有两种同步形式分别是同步方法也同步块。

4.线程死锁，

代码示例：

class MultiThread {
public static void main(String[] args) {
SellThread st = new SellThread();
new Thread(st).start();
try {
Thread.sleep(1);
}
catch(Exception e) {
e.printStackTrace();
}
st.b = true;
new Thread(st).start();
//new Thread(st).start();
//new Thread(st).start();

}

}
class SellThread implements Runnable {

int tickets = 100;
boolean b = false;
Object obj = new Object();
public void run() {
if(b == false) {
while(true) {
sell();
}
}
while(true) {
synchronized(obj) {//obj----this
try {
Thread.sleep(10);
}
catch(Exception e) {
e.printStackTrace();
}
synchronized(this) {
if(tickets>0) {
System.out.println("obj" + Thread.currentThread().getName() + "sell tickets:" + tickets);
tickets--;
}
}
}
sell();
}
}
public synchronized void sell() {
if(tickets>0) {
synchronized(obj) {
try {
Thread.sleep(10);
}
catch(Exception e) {
e.printStackTrace();
}
System.out.println("this" + Thread.currentThread().getName() + "sell tickets:" + tickets);
tickets--;
}
}
}
}

上面两个线程互相等待各自的锁所以会出现死锁现象

5.wait() 与 notify();

代码示例：

class Test {
public static void main(String[] args) {
Queue q = new Queue();
Producer p = new Producer(q);
Consumer c = new Consumer(q);
p.start();
c.start();
}

}
class Producer extends Thread {
Queue q;
Producer(Queue q) {
this.q = q;
}
public void run() {
for(int i=0;i<10;i++) {
q.put(i);
System.out.println("Producer put" + i);
}
}
}

class Consumer extends Thread {
Queue q;
Consumer(Queue q) {
this.q = q;
}
public void run() {
while(true) {
System.out.println("Consumer:" + q.get());
}

}
}
class Queue {
int value;
boolean b = false;
public synchronized void put(int i) {
if(b == false) {
value = i;
b = true;
notify();
}
try{
wait();
}
catch(Exception e) {
e.printStackTrace();
}
}
public synchronized int get() {
if(b == false) {
try {
wait();
}
catch(Exception e) {
e.printStackTrace();
}
}
b = false;
notify();
return value;

}

}