以下有一个java程序内容：
package javatest1;

import java.util.ArrayList;
import java.util.List;

public class javatest1 extends common{

    /**
     * @param args
     */   
    public static void main(String[] args) {
        // TODO Auto-generated method stub
             /* String c="Hello World!";  
              String d="您好!";
              String e="0123456789";
              stringchangeasc(c);
              printseparator();
              stringchangeasc(d);
              printseparator();
              stringchangeasc(e);
              printseparator(); */              
              String c="Hello World";
              int cai = 0;
              char[] ca;              
              List cb=new ArrayList();            
              ca = c.toCharArray();                  
              for(int i=0;i<ca.length;++i)
                 {
                     cai=ca[i]+32;   
                     cb.add(cai);               
                    }         
              print(cb);
    }
            
}
以下是common类内容：
package javatest1;

public class common {
   
    //简单打印
    public static <E> void print(E value)
    {
        System.out.println(value);
    }

    //字符串每个字符变成ascii码
    public static void stringchangeasc(String value)
    {
         char[] ca;
         int cai;
         ca = value.toCharArray(); //把传过来的value转换为字符数组           
         for(int i=0;i<ca.length;++i)
         {
             cai=ca[i];
             print(ca[i]+"的ascii码是"+cai);            
         }           
    }
   
    //如果输出内容是不同部分的话，用************************************隔开   
    public static void printseparator()
    {
        print("************************************");
    }

}
其中javatest1类我想实现一个字符串"Hello World"的全部字符如果是大写就变成小写即"HELLOWORLD"变成"helloworld",其中javatest1类我只能写到把字符串变成字符数组后，把字符数组每一个ascii加上32后，就没有办法把变化的ascii变回相应的字符，如果有另外其它办法把字符串"Hello World"的全部字符如果是大写就变成小写即"HELLOWORLD"变成"helloworld"也可以提出来(要给出程序来)，我终极目标是把字符串的全部字符中如果是大写变成小写，小写变成大写，其它字符不变，如果有这个程序也可以给出，谢谢！

各位高手们不要你们了，我已解决这个问题了，以下是解决这个问题的程序：
package javatest1;

import java.util.ArrayList;
import java.util.List;

public class javatest1 extends common{

    /**
     * @param args
     */   
    public static void main(String[] args) {
        // TODO Auto-generated method stub
             /* String c="Hello World!";  
              String d="您好!";
              String e="0123456789";
              stringchangeasc(c);
              printseparator();
              stringchangeasc(d);
              printseparator();
              stringchangeasc(e);
              printseparator(); */              
              String c="Hello World! Welcome China![520]";
              int cai = 0;
              char[] ca;              
              List cb=new ArrayList();            
              StringBuilder sb=new StringBuilder();
              ca = c.toCharArray();              
              for(int i=0;i<ca.length;++i)
                 {
                  if(ca[i]>65 && ca[i]<90)
                  {
                      cai=ca[i]+32;
                  }
                  else
                      if(ca[i]>97 && ca[i]<122)
                      {
                          cai=ca[i]-32;
                      }
                      else
                      {
                          cai=ca[i];
                      }
                     //cai=ca[i]+32;   
                     cb.add(cai);               
                    }         
              for(int j=0;j<cb.size();++j)
                 {
                      int obji=(int) cb.get(j);                        
                      char oi=(char)obji;
                      sb.append(oi);                  
                    }   
              print(sb);              
           
    }
            
}
以下是common类的内容：
package javatest1;

public class common {
   
    //简单打印
    public static <E> void print(E value)
    {
        System.out.println(value);
    }

    //字符串每个字符变成ascii码
    public static void stringchangeasc(String value)
    {
         char[] ca;
         int cai;
         ca = value.toCharArray(); //把传过来的value转换为字符数组           
         for(int i=0;i<ca.length;++i)
         {
             cai=ca[i];
             print(ca[i]+"的ascii码是"+cai);            
         }           
    }
   
    //如果输出内容是不同部分的话，用************************************隔开   
    public static void printseparator()
    {
        print("************************************");
    }
   


}