calceng.java

使用java实现的计算器程序.拥有简单的计算功能,如开方,平方等.

///////    CalcEng.java    ///////

class CalcEng
{   
// public members

   public CalcEng() {   allClear();  }

   public String keys() { return KEYS; }
   public byte precision() { return PREC; }

   public char getOpcode()     // returns current opcode
   {  return op;  }

   public double getOutput()   // returns current argument
   { return( argcnt==2 ? arg : ans ); }


   public void operate(char nc)         // nc is next opcode
   {   switch( nc )
       {  case 'A': allClear(); return; // All Clear
          case 'C': clear(); return;    // Clear
          case 'N':                     // sign change
                    if ( argcnt == 1 ) 
                         ans = -ans;
                    else arg = -arg;
                    return;
          default :                     // +-*/=
                    compute();
                    op = nc;            // new opcode
       }
   }

   public void setOperand(double in) 
   {   if ( op == '=' )
           ans = in;
       else
       {   arg = in;
           argcnt = 2;
       }
   }

   public static void CalcInfo()
   {
	   System.out.println("Please choose calculate mode:");
	   System.out.println("1.Basic mode");
	   System.out.println("2.Memory mode");
   }
//former private method
   protected void compute()
   {  if ( argcnt == 2 )
      {  switch( op )
         {   case '+':  ans += arg; break;
             case '-':  ans -= arg; break;
             case '*':  ans *= arg; break;
             case '/':  ans /= arg; break;
         }
         argcnt = 1;
      }
   isError(ans);
   }
   
   public String status()
   {
	   return statusFlag;
   }
   
   public boolean isError()
   {
	   if(statusFlag.equals(ERROR))
			return true;
		else
			return false;	
	}
//former private method
   protected void isError(double n)
   {
	   if(Math.abs(n) > MAX_VALUE || Double.isInfinite(n) || Double.isNaN(n))
		   statusFlag = ERROR;	
		else
			statusFlag = OK;
   }
//former private method   
   protected void allClear()
   {  ans = arg = 0.0; 
      argcnt = 1;
      op = '=';
      statusFlag = OK;
   }
//former private method
   protected void clear()
   {
	   if ( argcnt == 1 ) 
       {   ans = 0.0; 
           op = '=';
       }
       else 
       {   arg = 0.0; 
           argcnt = 1;
       }
	   statusFlag = OK;
   }
//former private members
   private final String KEYS = "+-*/=NAC";
   private final byte PREC = 8;
   protected double ans, arg;
   protected char op;             // operation code
   protected int argcnt;          // argument count
   protected final String OK = "";
   protected final String ERROR = "E";
   protected String statusFlag = OK;
   protected final double MAX_VALUE = 99999999;

   public static void main(String[] args)
   {   CalcEng cal = new CalcEng();
       cal.setOperand(9.8);
       cal.operate('+');
       cal.setOperand(1.2);
       cal.operate('/');
       cal.setOperand(2.0);
       cal.operate('=');
       System.out.println(cal.getOutput());
   }
}