java 复用类

java 组合语法
package javahaonan;

class WaterSource{
        private String s ;
       WaterSource(){
              System. out.println("WaterSource()" );
               s= "Constructed";
       }
public String toString(){return s; }
}

public class SprinklerSystem {
private String valve1 , valve2 , valve3 , valve4 ;
private WaterSource source =new WaterSource();
private int i ;
private float f ;
        public String toString() {
return
               "valve1 = " + valve1 + " " +
           "valve2 = " + valve2 + " " +
               "valve3 = " + valve3 + " " +
           "valve4 = " + valve4 + "\n" +
               "i = "+ i +  " " + "f = " +f + " " +
           "source = " + source ;
              }
        public static void main(String[] args) {
              SprinklerSystem sprinklers = new SprinklerSystem();
              System. out.print(sprinklers);
       }

}
/*
WaterSource()
valve1 = null valve2 = null valve3 = null valve4 = null
i = 0 f = 0.0 source = Constructed
*/
toString()每一个非基本类型的对象都有一个toSting的方法，当编译器需要一个String时而你却只有一个对象时，该方法就会被调用。"source = " + source 是将一个source对象 "source=“同WaterSource相加。由于只能将一个 String同另一个 String相加，因此会调用WaterSource的toString(),把source转换成为一个sting。而后将两个string连接到一起并传给System.out.print()。基本类型会被初始化为零，对象的饮用会被初始化为null。
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
package javahaonan;
import static javahaonan.Print.*;

class Soap{
        private String s ;
       Soap(){
               print("Soap()");
               s= "Constructed";
              }
        public String toString(){return s;}
}
public class Bath {
private String s1 ="Happy" , s2 ="sd" ,s3 ,s4 ;
       private Soap castille;
       private int i ;
       private float toy ;
   public Bath(){
          print("Inside Bath()");
          s3= "Joy";
          toy=3.14f;
          castille= new Soap();
          }
   {i=47;}
   public String toString(){
          if(s4 ==null)
                 s4= "Joy";
          return
                        "s1 ="+s1 + " " +
                  "s2 ="+ s2 + " " +
                        "s3 ="+ s3 + " " +
               "s4 ="+ s4 + " " +
                        "i= "+ i + " " +
               "toy="+ toy + " " +
                        "castille="+ castille ;
   }
   public static void main(String[] args) {
 Bath b = new Bath();
 print (b);

       }

}
/*
Inside Bath()
Soap()
s1 =Happy s2 =sd s3 =Joy s4 =Joy i= 47 toy=3.14 castille =Constructed
 
 */
四种初始化引用位置的示例，1、private String s1="Happy"在定义对象的地方初始化。2、在类构造其中初始化 s= "Constructed" ;。3、在使用对象之前初始化，惰性初始化Delayed initialization   if (s4 == null) s4= "Joy" ;4、使用实例初始化{ i=47;}。
print(b); 将return值传递给 print方法。  
"castille=" + castille ;当我需要将一个String对象却只有一个对象时，会调用Soap 中的 toString（）方法。
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
package javat;
class A{}
public class VarArgs {
  static void printArray(Object[] args){
         for(Object obj : args)
                System. out.print(obj+" " );
         System. out.println();
  }
        public static void main(String[] args) {
               printArray(new Object[]{
                            new Integer(47),new Float(32.12),332.2,new Double(3.321)
              });
               printArray(new Object[]{
                            "one","wang" ,"zi"
              });
        printArray(new Object[]{
                      new A(),new A(),new A()
        });
       }
}/*
47 32.12 332.2 3.321
one wang zi
javat.A@653cca0e javat.A@79f5910e javat.A@69066caf
*/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
package javat;

import static javat.Print.*;

class Soap {
        private String s ;
       Soap(){
               print("Soap()");
               s= "Constructed";
       }
        public String toString() {return s;}
}


public class Bath {
private String s1 ="Happy" ,s2 ="Happy" ,s3 ,s4 ;
private Soap castille ;
private int i ;
private float toy ;
public Bath(){
       print("Inside Bath()" );
        s3= "Joy";
        toy=3.14f;
        castille= new Soap();
}

{i=4;}
public String toString(){
        if(s4 ==null)
               s4= "Joy";
        return
                      "s1="+ s1 +"\n" +
               "s2="+ s2 + "\n" +
                      "s3="+ s3 + "\n"
            + "i="+i +"\n" +
                      "toy="+toy +"\n" +
            "castille="+ castille ;
}
        public static void main(String[] args) {
               print("wangzi");
         Bath b= new Bath();
         print(b);

       }

}
/*
wangzi
Inside Bath()
Soap()
s1=Happy
s2=Happy
s3=Joy
i=4
toy=3.14
castille=Constructed
*/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
package javat;
import static javat.Print.*;

class Cleanser{
        private String s ="Cleanser" ;
        public void append(String a) {s+=a;}
    public void dilute() {append("dilute()" );}
    public void apply() { append("apply()" );}
    public void scrub() {append ("scrub()" );}
    public String toString(){ return s ;}
 public static void main(String[] args){
        Cleanser x= new Cleanser();
        x.dilute();x.apply();x.scrub();
        print(x);
 }
}

public class Detergent extends Cleanser{
public void scrub(){
       append( "Detergent.scrub()");
        super.scrub();
}
public void foam() {append("foam()");}

        public static void main(String[] args) {
              Detergent x= new Detergent();
              x.dilute();
              x.apply();
              x.scrub();
              x.foam();
               print(x);
               print("Testing base class:");
              Cleanser. main(args);

       }

}
/*
Cleanserdilute()apply()Detergent.scrub()scrub()foam()
Testing base class:
Cleanserdilute()apply()scrub()
*/