如果以前曾詢問過此問題,但我不知道要搜索什麼,所以我很抱歉。Java子類化通用參數
不管怎樣,我正在做一個數學包,和許多類的擴展功能:
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);
}
我想比較功能,看看他們是平等的。如果他們來自同一個類,我想使用它的特定比較方法,但是如果他們是不同的類,我想返回false。這裏是其中的一個類我目前:
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;
}
}
我怎樣才能做到這一點?
你應該考慮的對象比較空,以避免收到'NPE' – user1406062
這八九不離十看起來像http://stackoverflow.com/questions/tagged/crtp的情況下, - 你可能想看看涉及java的相關問題,如http://stackoverflow.com/questions/2165613/java-generic-type也見:http://en.wikipedia.org/wiki/Talk%3ACuriously_recurring_template_pattern –
你可能只是想'公共抽象類功能' –
newacct