Gen.java Source code

Introduction

Here is the source code for Gen.java

Source

/*
Java 2, v5.0 (Tiger) New Features
by Herbert Schildt
ISBN: 0072258543
Publisher: McGraw-Hill/Osborne, 2004
*/

class Gen<T> {
    T ob; // declare an object of type T  

    // Pass the constructor a reference to   
    // an object of type T.  
    Gen(T o) {
        ob = o;
    }

    // Return ob.  
    T getob() {
        return ob;
    }
}

// Demonstrate raw type. 
public class RawDemo {
    public static void main(String args[]) {

        // Create a Gen object for Integers. 
        Gen<Integer> iOb = new Gen<Integer>(88);

        // Create a Gen object for Strings. 
        Gen<String> strOb = new Gen<String>("Generics Test");

        // Create a raw-type Gen object and give it 
        // a Double value. 
        Gen raw = new Gen(new Double(98.6));

        // Cast here is necessary because type is unknown. 
        double d = (Double) raw.getob();
        System.out.println("value: " + d);

        // The use of a raw type can lead to runtime. 
        // exceptions.  Here are some examples. 

        // The following cast causes a runtime error! 
        //    int i = (Integer) raw.getob(); // runtime error 

        // This assigment overrides type safety. 
        strOb = raw; // OK, but potentially wrong 
        //    String str = strOb.getob(); // runtime error  

        // This assignment also overrides type safety. 
        raw = iOb; // OK, but potentially wrong 
        //    d = (Double) raw.getob(); // runtime error 
    }
}