Question

我有以下课程：

package query;

public class Predicate<T> {

    private String operand1; 
    private String operator; 
    private T operand2; 
    private Class<T> classType; 

    public Predicate(String operand1, T operand2, Class<T> classType){
        this(operand1, "=", operand2, classType); 
    }

    public Predicate(String operand1, String operator, T operand2, Class<T> classType){
        this.operand1 = operand1; 
        this.operator = operator; 
        this.operand2 = operand2; 
        this.classType = classType; 
    }

    public String getOperand1() {
        return operand1;
    }

    public String getOperator() {
        return operator;
    }

    public T getOperand2() {
        return operand2;
    }

    public Class<T> getClassType() {
        return classType;
    }

    @Override
    public String toString() {
        return operand1 + " " + operator + " ?"; 
    }
}

以下行编译正常：

Predicate<String> p1 = new Predicate<>("given_name", "=", "Kim", String.class);

但是，以下情况并非如此：

Predicate<Integer> p1 = new Predicate<>("id", "=", "1", Integer.class);

编译器提到：无法推断Predicate＆lt;＆gt;

的类型参数

有什么问题/如何解决这个问题？

Answer 1

“1”是一个字符串，与Integer.class

不兼容

new Predicate<>("id", "=", 1, Integer.class)

应该没问题

或

new Predicate<>("id", "=", "1", String.class)

将Integer.class作为参数传递

1 个答案: