public class SprinklerSystem {
	private String valve；

	public String toString() {
		value = http://www.mamicode.com/"test";>
2. Java会自动在子类的构造器中插入对父类构造器的调用，即会先调用父类的构造器，如果父类没有无参的构造器，那就要通过super(param)显式调用父类带参构造器
class Art {
	Art() {
		print("Art constructor");
	}
}

class Drawing extends Art {
	Drawing() {
		print("Drawing constructor");
	}
}

public class Cartoon extends Drawing {
	public Cartoon() {
		print("Cartoon constructor");
	}

	public static void main(String[] args) {
		Cartoon x = new Cartoon();
	}
} 
/* Output:
Art constructor
Drawing constructor
Cartoon constructor
*///:~

3. 不能认为一个变量是final的，就认为无法改变它的值，final的意思是无法将引用只想另一个新的对象。
public class FinalArguments {
	void with(final Gizmo g) {
		//! g = new Gizmo(); // Illegal -- g is final
	}
}

4. 继承及初始化：
访问Beetle.main()方法时，加载器开始启动并找到Beetle类的编译代码，在对它进行加载的过程中，编译器注意到它有一个父类。
于是开始加载父类，然后父类中的static初始化即会被执行...
class Insect {
	private int i = 9;
	protected int j;

	Insect() {
		print("i = " + i + ", j = " + j);
		j = 39;
	}

	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");

	public Beetle() {
		print("k = " + k);
		print("j = " + j);
	}

	private static int x2 = printInit("static Beetle.x2 initialized");

	public static void main(String[] args) {
		print("Beetle constructor");
		Beetle b = new Beetle();
	}
} 
/* Output:
static Insect.x1 initialized
static Beetle.x2 initialized
Beetle constructor
i = 9, j = 0
Beetle.k initialized
k = 47
j = 39
*///:~


Think in Java(四)：复用类