在复习Thinking in java的过程中看到了相关内容，顺便整理一下，像下面一样的代码具体的执行顺序（ABCD都是类）
public class A {
public A(String text){
System.out.println("A was built :"+text);
}
D b1=new D("d in A");
static{
System.out.println("A Static Code out of constructor");
}
static D b2=new D("static b in A");
{
System.out.println("A Code out of constructor");
}
}
之前自己已经知道了，今天复习《Thinking in Java》又看到了这一段，在这里用代码来看看结果。最后给大家一个结论 代码如下（虽然有点长，但是仔细看还是挺简单的）
public class A {
public A(String text){
System.out.println("A was built :"+text);
}
D b1=new D("d in A");
static{
System.out.println("A Static Code out of constructor");
}
static D b2=new D("static b in A");
{
System.out.println("A Code out of constructor");
}
}
class B extends A{
static{
System.out.println("B Static Code out of constructor");
}
{
System.out.println("B Code out of constructor");
}
public B(String text){
super(text);
System.out.println("B was built :"+text);
}
}
class D{
public D(String text){
System.out.println("D was built :"+text);
}
public static void fsdaf(){
}
}
class C{
static{
System.out.println("C static code out of constructor");
}
public C(String text){
System.out.println("C was built :"+text);
}
}
class TestABC{
public static void main(String[] args) {
// A testA=null;
A testA=new A("testA");
System.out.println("********************************");
A testAf=new A("testA");
System.out.println("--------------------------------");
B testB=new B("testB");
System.out.println("********************************");
C testC=new C("testC");
}
}
结果如下
A Static Code out of constructor D was built :static b in A D was built :d in A A Code out of constructor A was built :testA ******************************** D was built :d in A A Code out of constructor A was built :testA -------------------------------- B Static Code out of constructor D was built :d in A A Code out of constructor A was built :testB B Code out of constructor B was built :testB ******************************** C static code out of constructor C was built :testC
从上面可以看出，如果没有继承父类 那么执行的顺序是
1.static类型的对象和代码段(那个在前面先执行哪个 且该类没有被实例化过)
2.类中非static的代码段
3.构造函数 如果该类已被实例化过，那么static的内容就不会再次被执行。
如果继承了父类 那么执行顺序是
1.父类中static类型的对象和代码段(哪个在前面先执行哪个 且该类没有被实例化过)
2.子类中的static类型的对象和代码段(哪个在前面先执行哪个 且该类没有被实例化过)
3.父类中的代码段
4.父类的构造函数
5.子类中的非静态代码段
6.子类构造函数
另外static的内容并不是代码写好就已经被执行，而是必须在使用到、类加载或者实例化的时候才会运行，这一点需要注意