Java The Complete Reference, Seventh Edition

To better understand how erasure works, consider the following two classes:

// Here, T is bound by Object by default.

class Gen<T> {

T ob; // here, T will be replaced by Object

Gen(T o) {

ob = o;

}

// Return ob.

T getob() {

return ob;

}

}

// Here, T is bound by String.

class GenStr<T extends String> {

T str; // here, T will be replaced by String

GenStr(T o) {

str = o;

}

T getstr() { return str; }

}

After these two classes are compiled, theTinGenwill be replaced byObject. TheTin

GenStrwill be replaced byString. You can confirm this by runningjavapon their compiled

classes. The results are shown here:

class Gen extends java.lang.Object{

java.lang.Object ob;

Gen(java.lang.Object);

java.lang.Object getob();

}

class GenStr extends java.lang.Object{

java.lang.String str;

GenStr(java.lang.String);

java.lang.String getstr();

}

Within the code forGenandGenStr, casts are employed to ensure proper typing. For

example, this sequence:

Gen<Integer> iOb = new Gen<Integer>(99);

int x = iOb.getob();

would be compiled as if it were written like this:

350 Part I: The Java Language