下面是Think in Java中的一段代码,自己加了几行
package reusing;
import static net.mindview.util.Print.*;
class Insect {
private int i = 9;
protected int j;
private int x2 = printInit("Insect.x1 initialized");
Insect() {
print("i = " + i + ", j = " + j);
j = 39;
}
static {
System.out.println("Init Static block");
}
{
System.out.println("Init block");
}
private static int x1 = printInit("static Insect.x1 initialized");
static int printInit(String s) {
print(s);
return 47;
}
}
public class Beetle extends Insect {
private int k = printInit("Beetle.k initialized");
static {
System.out.println("Beetle static block");
}
public Beetle() {
print("k = " + k);
print("j = " + j);
}
private static int x2 = printInit("static Beetle.x2 initialized");
private int x1 = printInit("Beetle.x2 initialized");
public static void main(String[] args) {
print("Beetle constructor");
Beetle b = new Beetle();
}
}
分析其类加载的过程:
(1)首先加载当前类,再加载当前类的父类,直到加载到基类,然后执行基类的static代码块,再执给基类里面的static成员变量赋值,赋值完成之后再执行子类里面的static代码块和给static成员变量赋值,以此类推。
(2)static块和成员赋值为完成之后回到基类中,给其余的非static的成员变量赋值,再执行非静态块,然后是构造方法,完成之后回到子类中继续按(2)处执行
上面的代码执行结果是:
Init Static block
static Insect.x1 initialized
Beetle static block
static Beetle.x2 initialized
Beetle constructor
Insect.x1 initialized
Init block
i = 9, j = 0
Beetle.k initialized
Beetle.x2 initialized
k = 47
j = 39
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