如果以前曾询问过此问题,但我不知道要搜索什么,所以我很抱歉。Java子类化通用参数
不管怎样,我正在做一个数学包,和许多类的扩展功能:
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);
}
我想比较功能,看看他们是平等的。如果他们来自同一个类,我想使用它的特定比较方法,但是如果他们是不同的类,我想返回false。这里是其中的一个类我目前:
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;
}
}
我怎样才能做到这一点?
你应该考虑的对象比较空,以避免收到'NPE' – user1406062
这八九不离十看起来像http://stackoverflow.com/questions/tagged/crtp的情况下, - 你可能想看看涉及java的相关问题,如http://stackoverflow.com/questions/2165613/java-generic-type也见:http://en.wikipedia.org/wiki/Talk%3ACuriously_recurring_template_pattern –
你可能只是想'公共抽象类功能' –
newacct