线程安全的单例模式

/**
 * @author z_hou
 * @create 2019-07-05-11:16
 */
public class BankTest {
}

class Bank{
    //私有化构造器
    private Bank(){}
    private static Bank instance = null;

    public static Bank getInstance() {
        if(instance == null){
            synchronized (Bank.class){
                if(instance == null){
                    instance = new Bank();
                }
            }
        }
        return instance;
    }
    
}