answerWhich of these packages contains abstract keyword?Optionsjava.langjava.iojava.utiljava.system

The abstract keyword in Java is used to declare a class that cannot be instantiated or to declare a method without an implementation. In terms of the given options, none of the packages explicitly contain the abstract keyword; however, the option that is most relevant to abstract classes is java.util since it contains several abstract classes, such as AbstractList, AbstractSet, etc.

To clarify:

1. java.lang: This is the fundamental package that contains essential classes but does not define abstract classes containing the keyword.
2. java.io: This package provides classes for input and output but does not directly define the abstract keyword as part of its primary classes.
3. java.util: This package contains various abstract classes and interfaces commonly used in Java programming (e.g., AbstractCollection, AbstractList).
4. java.system: This is not a standard Java package.

Final Answer

The package that most closely aligns with containing the use of the abstract keyword is java.util.