Java初始化顺序

import static net.mindview.util.Print.*;
class Glyph {
　　void draw() { print("Glyph.draw()"); }
　　Glyph() {
　　　　print("Glyph() before draw()");
　　　　draw();
　　print("Glyph() after draw()");
　　}
}
class RoundGlyph extends Glyph {
　　private int radius = 1;
　　RoundGlyph(int r) {
　　　　radius = r;
　　　　print("RoundGlyph.RoundGlyph(), radius = " + radius);
　　}
　　void draw() {
　　　　print("RoundGlyph.draw(), radius = " + radius);
　　}
}
public class PolyConstructors {
　　public static void main(String[] args) {
　　　　new RoundGlyph(5);
　　}
} 

/* Output:
Glyph() before draw()
RoundGlyph.draw(), radius = 0
Glyph() after draw()
RoundGlyph.RoundGlyph(), radius = 5

 

《Thinking in Java》说：

1. The storage allocated for the object is initialized to binary zero before anything else
happens.
2. The base-class constructors are called as described previously. At this point, the
overridden draw( ) method is called (yes, before the RoundGlyph constructor is
called), which discovers a radius value of zero, due to Step 1.
3. Member initializers are called in the order of declaration.
4. The body of the derived-class constructor is called.

 

由3可知，方法继承发生在构造器之前