带有泛型类的大十进制

Question

不兼容的边界编译错误

public class Complex<T extends  BigDecimal, R extends BigDecimal> {

    private T r;
    private R i;    
    
    public Complex(T r, R i) {
        this.r = r;
        this.i = i;
    }
    
    @Override
    public String toString() {
        return "Complex{" + "r=" + r + ", i=" + i + '}';
    }
    
    public T getR() {
        return r;
    }
    
    public R getI() {
        return i;
    }
    
    public Complex<T,R> add (Complex<T,R> other){
        return new Complex<T,R>((T) (r.add(other.r)), (R) (i.add(other.i)));
    }
}

然后调用类构造函数时：

Complex<BigDecimal,BigDecimal> s = new Complex<>(12121,12121);

出现这个编译错误：

cannot infer type arguments for Complex<>
  reason: inference variable T has incompatible bounds
    upper bounds: BigDecimal
    lower bounds: Integer
  where T is a type-variable:
    T extends BigDecimal declared in class Complex

Answer 1

Java 不会将

int

隐式转换为

BigDecimal

，您需要显式向构造函数参数提供 BigDecimal 类型。

Complex<BigDecimal,BigDecimal> s = new Complex<>(BigDecimal.valueOf(12121),BigDecimal.valueOf(12121));