Java的执行顺序

Java类的执行顺序如下:(一般顺序)

1. 父类的静态数据和静态块的初始化
2. 子类的静态数据和静态块的初始化
3. 父类的非静态数据和非静态块的初始化
4. 父类的构造函数的执行
5. 子类的非静态数据和非静态块的初始化
6. 子类的构造函数的执行

见下:

package com.xiyou.test;

class Bowl {		
	static {
		System.out.println("\tBowl类:" + "静态初始化");
		System.out.println("\t-------------------");
	}
	
	{
		System.out.println("\tBow类:" + "非静态初始化块");
	}
	Bowl(int mark) {
		System.out.println("\tBowl构造函数, Bowl(" + mark + ")");
	}
	
	Bowl() {
		System.out.println("\tBowl构造函数");
	}
	
	void f1(int mark) {
		System.out.println("f1(" + mark + ")");
	}
}


class Cupboard extends Bowl {
	{
		System.out.println("----Cupboard类:" + "初始化块");
	}
	
	static {
		System.out.println("----Cupboard类:" + "静态初始化块");
	}
	
	Cupboard(int mark) {
		super(mark);
		System.out.println("-----Cupboard类:" + "构造函数\n");
	}
	
	Cupboard() {
		System.out.println("-----Cupboard类:" + "构造函数\n");
	}
}


public class StaticInitialization {
	static {
		System.out.println("测试开始");
	}
	
	public static void main(String[] args) {
	}
	
	static Cupboard cupboard = new Cupboard(1000);//与下面的语句打印的结果相似
	//static Cupboard cupboard = new Cupboard();//对于构造函数中是否第一条语句有super,最终都是执行super的. 
	
}
/*打印结果:
测试开始
	Bowl类:静态初始化
	-------------------
----Cupboard类:静态初始化块
	Bow类:非静态初始化块
	Bowl构造函数, Bowl(1000)
----Cupboard类:初始化块
-----Cupboard类:构造函数
 */

 

 

package com.xiyou.test;

class Bowl {
	static Bowl b = new Bowl(0);
		
	static {
		System.out.println("\tBowl类:" + "静态初始化");
		System.out.println("\t-------------------");
	}
	
	Bowl(int mark) {
		System.out.println("\tBowl构造函数, Bowl(" + mark + ")");
	}
	
	Bowl() {
		System.out.println("\tBowl构造函数");
	}
	
	void f1(int mark) {
		System.out.println("f1(" + mark + ")");
	}
}

class Table {
	int i = 3;
	
	{
		System.out.println("Table类:" + "顺序执行非静态变量和初始化块的初始化");
		System.out.println("变量i:" + i);
		//bow3.f1(1);  Cannot reference a field before it is defined
	}
	
	Bowl bow3 = new Bowl(3);
	
	static {
		System.out.println("Table类,顺序开始执行静态变量和静态方法块的初始化");
	}
	
	static Bowl bowl1 = new Bowl(1);

	Table() {
		System.out.println("Table类:" + "构造函数");
		bow3.f1(1);
	}
	
	void f2(int mark) {
		System.out.println("f2(" + mark + ")");
	}
	
	static Bowl bowl2 = new Bowl(2);
	
	static {
		System.out.println("Table类:" + "静态变量和静态初始化块初始完毕");
	}
}


public class StaticInitialization {
	static {
		System.out.println("测试开始");
	}
	
	public static void main(String[] args) {
		System.out.println("\n---main函数开始-------");
		table.f2(1);
		System.out.println("Create new Table() in main");
		System.out.println("---main函数结束-------");
	}
	 
	static Table table = new Table();
}

//无论创建多少个对象,静态数据只占用一份存储区域
//初始化的顺序是先静态对象(如果它们尚未因前面的对象创建过程而被初始化),而后是"非静态对象"
/*打印结果:
测试开始
Table类,顺序开始执行静态变量和静态方法块的初始化
	Bowl构造函数, Bowl(0)
	Bowl类:静态初始化
	-------------------
	Bowl构造函数, Bowl(1)
	Bowl构造函数, Bowl(2)
Table类:静态变量和静态初始化块初始完毕
Table类:顺序执行非静态变量和初始化块的初始化
变量i:3
	Bowl构造函数, Bowl(3)
Table类:构造函数
f1(1)

---main函数开始-------
f2(1)
Create new Table() in main
---main函数结束-------
*/