String objects in Java are immutable which means:

Which keyword is used to manually clean up memory in java?

Consider the following code: int i=aReader.read(); What is the true of the type of variable aReader?

Any source code valid for one version of Java is also valid for all previous versions of Java.

What is an abstract class?

In Math and other java.lang Classes, generally all methods are declared _.

Normally, to access a static member of a class such as Math.PI, you would need to specify the class "Math". What would be the best way to allow you to use simply "PI" in your code?

Which keyword lets you call the constructor of a parent class?

If you encounter UnsupportedClassVersionError it means the code was ___ on a newer version of Java than the JRE ___ it.

You get a NullPointerException. What is the most likely cause?

How does the keyword volatile affect how a variable is handled?