toString方法多項式

Question

這是一個toString方法，用於格式化多項式的項並將它們添加到字符串中。它的最終輸出就像是「+ 2x^2 + 2x + 1」。我會如何去除第一個加號？由於

//toString method for returning ReesePolynomials in polynomaial format(for ReeseClient) 
     public String toString() 
     { 
      String output = ""; 
      //the following are situations for formatting the output of each term and adding them to String output 
      for (int i = 0; i < TermLength; i++) // For the number of terms stated by the user earlier, values will be given for each ReeseTerm in the poly array 
      { 
       if (poly[i].getExpo() == 0 && poly[i].getCoeff() > 0)  
       { 
        output += " + " + poly[i].getCoeff(); 
       } 

       else if (poly[i].getExpo() == 0 && poly[i].getCoeff() < 0) 
       { 
        output += " " + poly[i].getCoeff(); 
       } 

       else if (poly[i].getCoeff() == 1 && (poly[i].getExpo() != 0 && poly[i].getExpo() != 1)) 
       { 
        output += " + x^" + poly[i].getExpo(); 
       } 

       else if (poly[i].getCoeff() == 1 && (poly[i].getExpo() == 1)) 
       { 
        output += " + x";  
       } 

       else if (poly[i].getExpo() == 1 && poly[i].getCoeff() > 0) 
       { 
        output += " + " + poly[i].getCoeff() + "x"; 
       } 

       else if (poly[i].getExpo() == 1 && poly[i].getCoeff() < 0) 
       { 
        output += " " + poly[i].getCoeff() + "x"; 
       } 

       else if (poly[i].getCoeff() < 0 && (poly[i].getExpo() > 1 || poly[i].getExpo() < -1)) 
       { 
        output += " " + poly[i].getCoeff() + "x^" + poly[i].getExpo(); 
       } 

       else if (poly[i].getCoeff() == 0) 
       {} 

       else 
       { 
        output += " + " + poly[i].getCoeff() + "x^" + poly[i].getExpo(); 
       } 

      } 

     return output;  // the final string output is returned to be printed when called upon in main 
     } 

Answer 1

你的回報語句之前，使用子方法：

output = output.substring(2); 

這給你從索引2到結束的所有字符。 http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

您面臨的問題通常稱爲fencepost問題或逐個錯誤。 http://en.wikipedia.org/wiki/Off-by-one_error

Answer 2

嘗試
output = output.subString(2);
return output;