- 初始化顺序
在类的内部，变量的定义先后顺序决定了初始化的顺序。即使变量定义散布于方法定义之间。他们任就会在任何方法（包括构造器）被调用之前得到初始化
public class init {
public static void main(String[] args) {
House house = new House();
house.print();
}
}
class Window{
Window(int math){
System.out.println("Window:\t"+math);
}
}
class House{
Window window1 = new Window(1);
House(){
System.out.println("House");
window3 = new Window(4);
}
Window window2 = new Window(2);
void print(){
System.out.println("print()");
}
Window window3 = new Window(3);
}
结果：
Window: 1
Window: 2
Window: 3
House
Window: 4
print()
- 静态变量的初始化
无论创建多少个变量 静态数据都只占用一份存储区域 static 不能应用于局部变量 因此他只能作用于域
public class InitStatic {
public static void main(String[] args) {
System.out.println("start print method Cupboard()");
new Cupboard();
System.out.println("start print method Cupboard()");
new Cupboard();
}
//首先执行
static Table table = new Table();
static Cupboard cupboard = new Cupboard();
}
class Bowl{
Bowl(int math){
System.out.println("Bowl()\t"+math);
}
void print1(int math){
System.out.println("print()\t"+math);
}
}
class Table{
static Bowl bowl1 = new Bowl(1);
Table(){
System.out.println("Table()");
}
void print2(int math){
System.out.println("print2()\t"+math);
bowl2.print1(1);
}
static Bowl bowl2 = new Bowl(2);
}
class Cupboard{
Bowl bowl3 = new Bowl(3);
static Bowl bowl4 = new Bowl(4);
Cupboard(){
System.out.println("Cupboard()");
bowl4.print1(2);
}
void print3(int math){
System.out.println("print3()\t"+math);
}
static Bowl bowl5 = new Bowl(5);
}
结果是：
Bowl() 1
Bowl() 2
Table()
Bowl() 4
Bowl() 5
Bowl() 3
Cupboard()
print() 2
start print method Cupboard()
Bowl() 3
Cupboard()
print() 2
start print method Cupboard()
Bowl() 3
Cupboard()
print() 2
- 显式的静态初始化
java允许将多个静态初始化动作组织成一个特殊的“静态子句”(也叫静态代码块)，与其他的静态初始化动作一样，这段代码仅执行一次：当首次生成这个类的对象时，或者首此访问属于哪个类的静态数据成员时
class Cup{
Cup(){
System.out.println("Cup()");
}
}
class Cups{
static Cup cup1;
static Cup cup2;
static{
cup1 = new Cup(1);
cup1 = new Cup(2);
}
}
- 非静态实例实例初始化（代码块初始化）
与静态初始化一样，只是少了一个static,代码块会在构造器执行之前先执行
class Cup{
Cup(){
System.out.println("Cup()");
}
}
class Cups{
Cup cup1;
Cup cup2;
{
cup1 = new Cup(1);
cup1 = new Cup(2);
}
}
