数据库 死锁的解决(转)

java中的super关键字具有以下两个功能

         1. 通过它可以在子类的构造方法中调用父类的某个构造方法，而且super()语句必须是子类构造方法中的头一条语句

             注意：如果在子类的构造方法中没有使用关键字super调用父类的某个构造方法，那么默认有super()；语句，即调用父类的不带

                      参数的构造方法(该构造方法不是父类中的默认构造方法，而是自定义的构造方法)

             eg:  class Student

                    {

                          Student(String name,int age)

                          {

                                 System.out.println("my name is "+name+", i am "+age);

                          }

                    }

 

                    class Uni_Student extends Student

                    {

                          Uni_Student(String name,int age,boolean b)

                          {

                                 super(name,age);

                                 System.out.println("婚否="+b);

                          }

                    }

 

                    public class class1_1

                    {

                           public static void main(String args[])

                           {

                                    Uni_Student aa=new Uni_Student("zhangsan",22,false);

                           }

                    }

                运行以后的结果为：

                         my name is zhangsan, i am 22

                         婚否=false

 

         2. 通过它可以使用被子类隐藏了的父类中的成员变量和方法，即：super.成员变量名   或    super.方法名

             eg:  class sum

                    {

                          int n;

                          float f()

                          {

                                 int sum=0;

                                 for(int i=0;i<=n;i++)

                                     sum=sum+i;

                                 return sum;

                          }

                    }

 

                    class average

                    {

                           int n;

                           float f()

                           {

                                 super.n=n;

                                 return super.f()/n;

                           }

 

                           float g()

                           {

                                 super.n=n;

                                 return super.f()/2;

                           }

                    }

 

                    public class class4_1

                    {

                           public static void main(String args)     

                    }