Java 中的泛型类

Question

I have three Classes:

1. Generic Class that has 3 fields - a boolean, a String for a message, and a T result.

2. A second class that is having the function to multiply two numbers passed as method parameters. The return type of this method is the generic class #1.

3. The third Class is the same as the second, but instead, I am concatenating two string parameters.

Question: How can my Generic class be used to display the result, the message, and the boolean for example, from Class #2?

Baiscally, Class.result should display the multiplied numbers.

public class ClassOne<T> {

    boolean success;
    String errorMessage;
    T result;
}

public class ClassTwo {

public ClassOne<Long> multiplyNumbers(Long num1, Long num2) {
}

}

Answer 1

You'll need to instantiate it with the generic type

public ClassOne<Long> multiplyNumbers(Long num1, Long num2) {
    ClassOne<Long> c = new ClassOne<>();
    try {
        Long multiplied = num1 * num2;
        c.setResult(multiplied);
    } catch (Exception e) {
        c.setError(e.getMessage());
    }
    return c;
}

For String concatenation, it would be the same, except I don't see how an exception could be thrown

public ClassOne<String> concatStrings(String string1, String string2) {
    ClassOne<Long> c = new ClassOne<>();
    c.setResult(string1 + string2);
    return c;
}