Java类初始化顺序

1）如果有父类，先初始化父类
2）类只被初始化一次，即类中的静态变量及静态代码块只在第一次加载时执行一次
3）类第一次初始化时先初始化静态变量，执行静态代码块
4）执行完静态代码后先初始化成员变量，然后执行构造器。

例：

package com.zsoft.test;

public class ClassLoadTest {
	public static void main(String[] args){
		new Circle();
	}
}

class Draw{
	public static String hello = "say hello!";

	static{
		System.out.println(hello);
	}
	
	public Draw(){
		System.out.println("draw construction");
	}
	
	public Draw(String type) {
		System.out.println(type + " draw construction");
	}
}


class Shape{
	public static Draw drawStatic = new Draw("shap static");
	private Draw draw = new Draw("shap");
	
	public Shape(){
		System.out.println("shap construction");
	}
}


class Circle extends Shape {
	private Draw draw = new Draw("circle");
	public static Draw drawStatic = new Draw("circle static");
	public Circle(){
		System.out.println("circle construction");
	}
}

输出：
say hello!
shap static draw construction
circle static draw construction
shap draw construction
shap construction
circle draw construction
circle construction