在Java中不指定原始类型就声明变量或将对象更改为其对应的原始类型

Question

I want to be able to declare a variable in Java, however I do not know what the type of the variable will be until an if, if else statement is evaluated.

I know that you can't declare the variable within each if statement because it will be out of scope outside of the if statement.

The variable also MUST be a primitive datatype instead of an object (eg Integer, Double, String)

// do not know datatype yet
(type) signalValue;

        // signal is Integer object
        if (SysjInput[1] instanceof Integer) {
                signalValue = (int) SysjInput[1];

        // signal is String object
        } else if (SysjInput[1] instanceof String) {
                signalValue = (String) SysjInput[1];

        // signal is Double object  
        } else if (SysjInput[1] instanceof Double) {
                signalValue = (double) SysjInput[1];
        }

System.out.println(signalValue)

I have also tried something like this:

Object signalValue;
signalValue = 123;

It will convert it to an Integer object and I would need some way to convert it to a primitive type.

Answer 1

Initializing with Object class should work, I tryed this and worked just fine:

    public static void main(String[] args) {

    Object t;

    t = 4;
    int d = (int) t;
    int e = d + d;

    System.out.println(e);
}

output: 8