What are 3 possible situations in which static methods might be included in classes?

I got this question for homework, and all开发者_高级运维 I can think of is to return a subclass of an abstract superclass.

Thanks!

Try looking at the existing Java APIs (eg: java.lang and java.util) to see where they use static methods.

Factory methods

• That return a particular instance like in a Singleton: java.lang.Runtime.getRuntime()
• That return a subclass of a super class as you mentioned: java.util.Calendar.getInstance()
• That perform type conversion: String.valueOf(int)

Utility methods

• In a class that also has instance methods : java.lang.String.format()
• In utility classes that are not meant to be instantiated at all: java.util.Arrays, java.lang.Math, java.util.Collections.

Generally methods which need not be tied to a specific object.

Factory methods.

Dont forget about using them to kick off the console applications we all had to write in cs101