class WaterSource{
	private String s;
	WaterSource(){
		System.out.println("WaterSource()");
		s="Contructed";
	}
	public String toString(){return s;}
}
public class SprinklerSystem {
private String value1,value2,value3,value4;
private WaterSource source=new WaterSource();
private int i;
private float f;
public String toString(){
	return 
	           "value1 = "+value1+" "+
	           "value2 = "+value2+" "+
	           "value3 = "+value3+" "+
	           "value4 = "+value4+"\n "+
	           "i = "+i+" "+"f = "+f+" "+
	           "source = "+source;
}
public static void main(String[] args){
	SprinklerSystem sprinker=new SprinklerSystem();
	System.out.println(sprinker);
}
}
/*
 * 在上面兩個類所定義的方法中，有一個很特殊：toString().每個非基本型別的物件都有一個toString()方法，而且當編譯器
 * 需要一個String而你只有一個物件時，該方法就會被呼叫。
 */

 

輸出：

WaterSource()
value1 = null value2 = null value3 = null value4 = null
 i = 0 f = 0.0 source = Contructed