troubleshooting Question

What is downcasting in Java?

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shampouya asked on
Java
13 Comments1 Solution688 ViewsLast Modified:
My textbook says "To access a specific method of the object, we must downcast to the correct type. (Of course, in this example we do not need the downcast, since we are simply invoking the toString method at line 9, and this can be done for any object). A second important detail is that primitive types cannot be used. Only reference types are compatible with Object"

I typed the body of the main method below, and I put the MemoryCell class in the code section. First of all, what does downcast mean? Second, I understand why primitive types like int and float can't be used, but why does my book say that the toString method is automatically invoked? Thirdly, there are some situations in which primitive types can be passed as arguments into methods of objects?

MemoryCell m = new MemoryCell();

m.write("37");
String val = (String) m.read();
System.out.println("Contents are: " + val);
//
//
//

public class MemoryCell
{
     //Public methods
     public Object read() {return storeValue;}
     public void write(Object x) {storedValue = x;}

     private Object storedValue;
}
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