对于我的作业，我需要使用由Term（我们之前在类中创建的类，例如：7x ^ 5）组成的ArrayList创建一个多项式类。我需要这样做，以便当术语插入ArrayList时，它们按降序排序。
这是我的代码：
public void insert(Term aTerm)
{
Term tempTerm = new Term(0,0); //term of 0x^0 that is used to set the term to 0 after its added.
if(aTerm == null)
throw new IllegalArgumentException("The inserted term cannot be null.");
else if(aTerm.isZero() == true)
aTerm.degree(); //PLACEHOLDER not sure what to do here in order to not insert aTerm
else if(aTerm.degree() > theAL.get(0).degree())
theAL.add(0, aTerm); //adds to position 0 if largest degree
else if(aTerm.degree() < theAL.get(theAL.size() - 1).degree())
theAL.add(theAL.size() - 1, aTerm); //adds to the last position if it is the smallest degree
else
for(int i = 0; i < theAL.size(); i++)
{
if(aTerm.isZero() == true)
i = theAL.size(); //ends the for loops whenever aTerm is added and set = to 0
else if(aTerm.degree() < theAL.get(i).degree() && aTerm.degree() > theAL.get(i + 1).degree())
{
theAL.add(i + 1, aTerm); //adds between 2 terms if less than 1st term and greater than 2nd term.
aTerm.multiplyBy(tempTerm); //makes the term = zero so that the for loop can end after being added.
}
else if(aTerm.degree() == theAL.get(i).degree())
{
aTerm.addIn(theAL.get(i)); //adds into the term if the degrees are equal
aTerm.multiplyBy(tempTerm);//makes the term = zero so that the for loop can end after being added.
}
}
}
如果该术语为0，我不希望它被添加到多项式中，但正如您在我的代码中看到的那样，我不确定我应该在那里做什么以便不插入它，所以我只是放了一个占位符在那里。我有什么想法吗？
当我将我的代码放入Instructors测试器时，只要它尝试添加术语，它就会抛出一堆OutOfBoundsException。
我理解OutOfBoundsException是什么，但我不确定是什么导致它在每个场景中超出范围。我知道我的代码可能需要很多工作，但如果有人能给我一些建议，我会非常感激。我努力想办法把它放在一起，特别是当我到达使用for循环遍历多项式的部分时，我一直在努力。
感谢您的帮助。
编辑：
术语等级：
public class Term implements TermInterface
//-------data
private int coefficient;
private int power;
//------constructors
//default constructor
public Term()
{
this.coefficient = 2;
this.power = 3;
}
//parameterized constructor
public Term(int aCoefficient, int aPower)
{
this.coefficient = aCoefficient;
this.power = aPower;
}
//copy constructor
public Term(Term aTerm)
{
if(aTerm != null)
{
this.coefficient = aTerm.coefficient;
this.power = aTerm.power;
}
else
throw new IllegalArgumentException("Term cannot be null");
}
//------methods
// toString() - returns its representation as a String 3x^2 for example,
public String toString()
{
if(this.coefficient == 0)
return "0";
else if(this.power == 0)
return(this.coefficient + "");
else if(this.coefficient == 1 && this.power == 1)
return "x";
else if(this.coefficient == -1 && this.power == 1)
return "-x";
else if(this.power == 1)
return(this.coefficient + "x");
else if(this.coefficient == 1)
return("x^" + this.power);
else if(this.coefficient == -1)
return("-x^" + this.power);
else
return(this.coefficient + "x^" + this.power);
}
//degree - if coefficient is 0, then (it is a constant so) returns 0.
// else returns the power
public int degree()
{
if(this.coefficient == 0)
{
return 0;
}
else
return power;
}
//evaluate - evaluates with whatever double is received
public double evaluate(double value)
{
return Math.pow(value, power) * this.coefficient;
}
//derivative - return a new Term that is the derivative. The derivative
// is calculated by:
// the coefficient of the derivative is the original coefficient times the power
// the power of the derivative is the original power minus 1
public Term derivative()
{
Term derivative = new Term(this.coefficient * this.power, this.power - 1);
return derivative;
}
//addIn: add another Term to itself.
//The Term that is received is not changed.
// if the Term that is received is null, throw a new IllegalArgumentException(<your descriptive String here>)
// if the powers are not the same, throw a new IllegalArgumentException(<your descriptive String here>)
public void addIn(Term anotherTerm)
{
if(anotherTerm == null)
throw new IllegalArgumentException("Term cannot be null");
else if(this.power != anotherTerm.power)
throw new IllegalArgumentException("Powers must be equial");
else
this.coefficient += anotherTerm.coefficient;
}
//multiplyBy: multiply itself by anotherTerm - result is a new Term that is created and returned.
//The original Term and the Term that is received are not changed.
// if the Term that is received is null, throw a new IllegalArgumentException(<your descriptive String here>)
public Term multiplyBy(Term anotherTerm)
{
if(anotherTerm != null)
throw new IllegalArgumentException("Term cannot be null");
else
{
Term multiplied = new Term(this.coefficient * anotherTerm.coefficient, this.power + anotherTerm.power);
return multiplied;
}
}
public boolean isZero()
{
if(this.coefficient == 0)
return true;
else
return false;
}
//equals: returns true if it is the same as what is received.
// If both coefficients are 0, they are automatically equal
// otherwise, both coefficients AND both exponents must be the same
public boolean equals(Object obj)
{
if (obj == null)
return false;
if (this.getClass() != obj.getClass())
return false;
Term objTerm = (Term)obj;
return(this.power == objTerm.power && this.coefficient == objTerm.coefficient);
}
}
编辑2： 最终工作代码：
public void insert(Term aTerm)
{
if(aTerm == null)
throw new IllegalArgumentException("The inserted term cannot be null.");
else if(aTerm.isZero() == true)
return;
int insertIndex = -1;
int i = 0;
boolean degreeEqual = false;
while(insertIndex == -1 && i < theAL.size())
{
Term tempTerm = theAL.get(i);
if(tempTerm.degree() == aTerm.degree())
{
degreeEqual = true;
aTerm.addIn(tempTerm);
insertIndex = i;
}
else if(aTerm.degree() > tempTerm.degree())
insertIndex = i;//ends the loop because we know where to put insert the term
i++; //increment index counter
}
if(degreeEqual == false)
{
if(insertIndex >= 0) //check to make sure index location is valid.
theAL.add(insertIndex, aTerm);
else
theAL.add(aTerm);//insert term at the end because it is less than other terms
}
else
{
if(insertIndex >= 0) //check to make sure index location is valid.
{
theAL.remove(insertIndex);
theAL.add(insertIndex, aTerm);
if(theAL.get(insertIndex).isZero())
{
theAL.remove(insertIndex);
}
}
else
theAL.add(aTerm);//insert term at the end because it is less than other terms
}
}
答案 0 :(得分：1)
我可以看到你要去哪里，但是你的测试和循环比你需要的要复杂得多。我可能会误解算法的意图，但我会简化为这样的事情：
inputType.zip(inputColName).zipWithIndex.map {
case (inputType, inputColName) =>
inputType match {
case (DoubleType, "col1") => println("test1")
case _ => println("test2")
}
}
答案 1 :(得分：0)
这条线很可能会导致一些问题：
else if(aTerm.degree() < theAL.get(i).degree() && aTerm.degree() > theAL.get(i + 1).degree())
您尝试访问列表中的i + 1元素。因为你的迭代遍历：
for(int i = 0; i < theAL.size(); i++)
这将导致内存访问＆＃34;一个更大的列表大小＆＃34;因此是一个OutOfBoundException。只是我的猜测，直到你可以分享你的Term课程。当列表为空（插入第一个元素之前）时，它也可能是一个问题，因为您访问列表中不存在的0元素。
根据null术语的其他问题：
else if(aTerm.isZero() == true)
aTerm.degree();
你可以return：
else if(aTerm.isZero() == true)
return;
如果没有任何事情可以做任何事情。