ArrayList不打印移除的对象

Question

public void delete (int coeff, int expo)
{
  for (int i = 0; i<terms.size(); i++)
  {
      Term current = terms.get(i);
      terms.remove(current.getCoeff());
      terms.remove(current.getExpo());
  }

}

public static void main(String[] args) throws IOException
{
    // TODO code application logic here
    Polynomial polyList = new Polynomial();



    Scanner inFile = new Scanner(new File("operations2.txt"));

    while(inFile.hasNext())
    {
       Scanner inLine = new Scanner(inFile.nextLine());

       String insert = inLine.next();

        if(insert.equals("INSERT"))
        {

           int coeff = inLine.nextInt();
           int expo = inLine.nextInt();            
           polyList.insert(coeff, expo);
        }
        if(insert.equals("DELETE"))
        {
            int coeff = inLine.nextInt();
            int expo = inLine.nextInt();
            polyList.delete(coeff, expo);
        }
    }
     System.out.println(polyList.toString());
   }
}

编辑：这是scanner类正在读取的。txt文件的示例：

INSERT 3 2
INSERT 4 4
INSERT 1 6
INSERT 2 0
INSERT 5 2
INSERT 6 3
PRODUCT
DELETE 3 2
INSERT 2 7
DELETE 4 4
INSERT 4 10

编辑：以下是术语类：

class Term
{
//instance vars
private int coefficient;
private int exponent;


 public Term(int coeff, int expo)
 {
  coefficient = coeff;
  exponent = expo;

 }
 public int getCoeff()
 {
   return coefficient;
 }
 public int getExpo()
 {
   return exponent;
 }
 @Override
 public int hashCode()
 {
   return  coefficient + exponent;
 }

   @Override
   public boolean equals(Object o)
   {

     if (!(o instanceof Term))
     {
       return false;
     }
     Term t = (Term)o;
     return coefficient == t.coefficient && exponent == t.exponent;
   }
}

Answer 1

如果delete()方法试图删除具有指定系数的Twrm，建议使用以下方法：

1. 重写equals()方法以返回true，如果参数是具有相同系数和指数的项
2. 重写hashcode()方法以返回基于相同两个值的哈希值

由于equals()方法应该进行值比较，这样的实现是非常合理的。

terms.remove(new Term(coeff, expo));

// in the Term class
@Override
public boolean equals(Object o) {
    if (!(o instanceof Term)
        return false;
    Term t = (Term)o;
    return coeff == t.coeff && expo == t.expo;
}

@Override
public int hashCode() {
    return 31 * coeff + expo;
}