多项式算术java等于方法

Question

我正在研究一个多项式计算器.我的问题是使用equals方法.这是相关代码:

public class Poly{
    Term[] terms;

    //Constructors-------------------------------------------
    public Poly() {}
    public Poly(ArrayList<Term> Terms) {
        terms = Terms.toArray(new Term[Terms.size()]);
        Arrays.sort(terms, new TermComparator());
    }

    //Methods-------------------------------------------------
    public boolean equals(Poly x) {
        boolean q=false;
        if(this == x){
            q=true;
        }
    return q;
    }

    //used in constructor to order terms
    class TermComparator implements Comparator<Term> {
        @Override
        public int compare(Term t1, Term t2) {
            return t2.getExp() - t1.getExp();
        }
    }
}

即使两个Poly对象具有相同的值,equals方法也始终返回false.有人可以帮忙吗？

Answer 1

您的Poly类equals方法应如下所示

@Override
public boolean equals(Object obj) {
    if (this == obj) //checking both are same instance
        return true;
    if (obj == null) // checking obj should not be null
        return false;
    if (getClass() != obj.getClass()) //checking both objects from same class
        return false;
    Poly other = (Poly) obj; 

    return Arrays.equals(terms, other.terms);  //checking all the array values
}

如果要将Poly对象添加到集合中,则还需要实现哈希代码方法.

    @Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + Arrays.hashCode(terms);
    return result;
}   

请参考

为什么我需要覆盖Java中的equals和hashCode方法？

使用JPA和Hibernate时应该如何实现equals和hashcode