Packages + java-visual

Which of the following classes is part of the java.awt package?

• System

• String

• ArrayList

• Button

Answer explanation

The correct answer is Button. The java.awt package contains classes that are used to create graphical user interfaces (GUIs). The Button class is a subclass of the Component class, and it is used to create buttons in a GUI. The other classes in the image are not part of the java.awt package.

Which of the following packages is the default package in the image?

• default package

• Hellojava

• rest

• SpringJSONRest Test

Answer explanation

The correct answer is default package. The default package is the package that is used when you do not specify a package name for your Java class. In the image, the RestletServer.java and RestletClient.java files do not have a package name specified, so they are part of the default package. The Hellojava and rest packages are both explicitly specified in the image, and the SpringJSONRest Test package is not a real package.

Which of the following statements about packages in Java is NOT true?

• Packages are used to organize Java classes and interfaces.

• Packages can be used to control access to Java classes and interfaces.

• Packages can be used to prevent name clashes between Java classes and interfaces.

• Packages are a required part of the Java language.

Answer explanation

The correct answer is Packages are a required part of the Java language. Packages are not a required part of the Java language. You can write Java programs without using packages, but you will not be able to take advantage of the benefits of packages, such as organization, access control, and name clashes.

Which line of code indicates to the compiler that the Person class belongs to the personpackage package?

• package personpackage;

• public class Person

• private String firstName;

• public String getFirstName()

Answer explanation

The correct answer is package personpackage;. The package statement is used to indicate to the compiler which package a Java class belongs to. In the image, the package personpackage; statement is on the first line of the Person.java file, which indicates that the Person class belongs to the personpackage package.

Which of the following classes is part of the java.lang package?

• System

• String

• ArrayList

• Button

Answer explanation

The correct answer is System. The java.lang package is the default package in Java, and it contains classes that are fundamental to the language, such as System and String. The other classes in the image are part of the util and awt packages.

Which of the following is the most common type of built-in package in Java?

• java.lang

• java.util

• java.awt

• java.io

Answer explanation

The correct answer is java.lang. The java.lang package is the default package in Java, and it contains classes that are fundamental to the language, such as System, String, and Object. The other packages in the image are all useful, but they are not as fundamental as the java.lang package.

Which of the following packages is not a sub-package of java.util?

• concurrent

• logging

• collections

• concurrency.concurrent

Answer explanation

The correct answer is concurrency.concurrent. The concurrency package is a sub-package of the java.util package, but the concurrency.concurrent package is not. The concurrency.concurrent package is a nested package, which is a special type of sub-package that is created by putting a period between the names of the packages.

Which of the following is the default package in Java?

• java

• lang

• util

• awt

Answer explanation

The correct answer is java. The java package is the default package in Java, and it contains all of the classes that are not explicitly placed in another package. The lang, util, and awt packages are all subpackages of the java package.

Which of the following is the name of the folder in the image?

• animals

• Animals

• animal

• animals.class

Answer explanation

The correct answer is animals. The image shows a folder named animals. The other answer choices are either incorrect capitalizations of the folder name, or they are the name of a file in the folder.

Which of the following classes is part of the java.util package?

• Date

• Calendar

• Object

• Applet

Answer explanation

The correct answer is Date. The java.util package contains classes that are used for data manipulation and date and time handling. The Date class is used to represent a specific point in time. The other answer choices are either classes that are not part of the java.util package, or they are not classes at all.