同步方法-买票的例子：

package com.kaka.thread;

import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

public class BuyTicket {
    public static void main(String[] args) {

        BuyT buyT=new BuyT();
        new Thread(buyT,"小明").start();
        new Thread(buyT,"老师").start();
        new Thread(buyT,"黄牛").start();
    }


}

class BuyT implements Runnable{
    private  int ticketNum=10;
    boolean flag=true;
    @Override
    public void run() {
        //买票
        while(flag){
            buy();
        }

    }
    //synchronized 同步方法 锁的是this
    private synchronized void buy(){
        if (ticketNum<=0){
            System.out.println("没票了！");
            flag=false;
        }
        else{
            System.out.println(Thread.currentThread().getName()+"抢到了第"+ticketNum--+"张票");
        }
    }
}

同步块-银行取钱的例子：

package com.kaka.thread;

//两个人去银行取钱，操作同一个账户
public class TestDrawing {
    public static void main(String[] args) {

        Account account=new Account("结婚基金",200);
        new Drawing(account,50,"wife").start();
        new Drawing(account,10,"husband").start();
    }
}

//账户
class Account{
    String accountName;
    int leftMoney;

    public Account(String name, int leftMoney) {
        this.accountName = name;
        this.leftMoney = leftMoney;
    }
}

//银行模拟取款
class Drawing extends Thread{
    Account account;
    int drawingMoney;
    String name;//取钱人的名字

    int nowMoney=0;

    public Drawing(Account account,int drawingMoney, String name){
        this.account=account;
        this.drawingMoney=drawingMoney;
        this.name=name;
    }

    @Override
    public void run() {
        //同步块
        synchronized (account){
            //判断有没有钱
            if(account.leftMoney<drawingMoney){
                System.out.println(account.accountName+"里钱不够，无法取钱");
            }else{
                account.leftMoney=account.leftMoney-drawingMoney;
                nowMoney=nowMoney+drawingMoney;//你手里的钱=取出的钱
            }

            System.out.println(name+"取走了:"+nowMoney);
            System.out.println(account.accountName+"账户余额为："+account.leftMoney);

        }
    }
}