Java generic method type casting

Question

Why this happened? One line in the code works well while the other similar line doesn't. Does the automatic type cast only happen in certain conditions? I have tried to assign gt.echoV() to an Object and it works well; but when I assign it to a String, the same error will come out again.

public class GeneMethodTest {

    public static void main(String... args) {
        GeneMethodTest gt = new GeneMethodTest();
        gt.<String>echoV(); //this line works well
        gt.<String>echoV().getClass();//this line leads to a type cast exception                                                          
    }

    public <T> T echoV() {
        T t=(T)(new Object());                                                                    
        return t;
    }
}

Answer 1

gt.<String>echoV().getClass(); produces the equivalent of the following sequence of operations:

// Inside echoV
Object t = new Object();  // Note that this is NOT a String!
Object returnValue = t;
// In main
String stackTemp = (String) returnValue;  // This is the operation that fails
stackTemp.getClass();

What you get "for free" with generics is that (String) cast. Nothing else.