doubts in java.lang Dbt #1

[omkar patkar]

According to java.lang "Process" is an Abstract class , also, we cannot instantiate "Runtime" class.......does it mean Runtime is also abstract class ?......How can a method of "Runtime" class (.....i.e., "exec()" ) return an object of "Process" class when we know that "Process" class is abstract and that it cannot be instantiated ?

[Ernest Friedman-Hill]

It doesn't return an object of Process class. It returns an object whose type is compatible with Process -- i.e, a package-private subclass of Process. This pattern shows up all over the Java APIs -- it's a very fundamental concept in object-oriented programming.