如果之前有人问过这个问题,我很抱歉,但我真的不知道要搜索什么。
无论如何,我正在制作一个数学包,并且许多类都扩展了 Function:
package CustomMath;
@SuppressWarnings("rawtypes")
public abstract class Function <T extends Function> {
public abstract Function getDerivative();
public abstract String toString();
public abstract Function simplify();
public abstract boolean equals(T comparison);
}
我想比较函数以查看它们是否相等。如果它们来自同一个类,我想使用其特定的比较方法,但如果它们属于不同的类,我想返回 false。这是我目前的类(class)之一:
package CustomMath;
public class Product extends Function <Product> {
public Function multiplicand1;
public Function multiplicand2;
public Product(Function multiplicand1, Function multiplicand2)
{
this.multiplicand1 = multiplicand1;
this.multiplicand2 = multiplicand2;
}
public Function getDerivative() {
return new Sum(new Product(multiplicand1, multiplicand2.getDerivative()), new Product(multiplicand2, multiplicand1.getDerivative()));
}
public String toString() {
if(multiplicand1.equals(new RationalLong(-1, 1)))
return String.format("-(%s)", multiplicand2.toString());
return String.format("(%s)*(%s)", multiplicand1.toString(), multiplicand2.toString());
}
public Function simplify() {
multiplicand1 = multiplicand1.simplify();
multiplicand2 = multiplicand2.simplify();
if(multiplicand1.equals(new One()))
return multiplicand2;
if(multiplicand2.equals(new One()))
return multiplicand1;
if(multiplicand1.equals(new Zero()) || multiplicand2.equals(new Zero()))
return new Zero();
if(multiplicand2.equals(new RationalLong(-1, 1))) //if one of the multiplicands is -1, make it first, so that we can print "-" instead of "-1"
{
if(!multiplicand1.equals(new RationalLong(-1, 1))) // if they're both -1, don't bother switching
{
Function temp = multiplicand1;
multiplicand1 = multiplicand2;
multiplicand2 = temp;
}
}
return this;
}
public boolean equals(Product comparison) {
if((multiplicand1.equals(comparison.multiplicand1) && multiplicand2.equals(comparison.multiplicand2)) ||
(multiplicand1.equals(comparison.multiplicand2) && multiplicand2.equals(comparison.multiplicand1)))
return true;
return false;
}
}
我该怎么做?
最佳答案
使用泛型,您可以保证 equals 方法仅适用于类型“T”,在本例中为“Product”。您无法传递其他类类型。
另一种可能性是在类函数定义中:
public abstract boolean equals(Function comparison);
在 Product 类中,对象与 comparison instanceof Product
进行比较
关于Java 子类化泛型参数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12764597/