Creating packages in Java - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a package named com.example.app.

Java

package [1];

Drag options to blanks, or click blank then click option'

Acom example app

Bcom_example_app

Ccom-example-app

Dcom.example.app

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscores or dashes instead of dots in package names.

Including spaces in the package declaration.

The package declaration uses dot notation without spaces or special characters.

2fill in blank

medium

Complete the code to import the class Utils from package com.example.utils.

Java

import [1].Utils;

Drag options to blanks, or click blank then click option'

Acom.example.utils

Bcom_example_utils

Ccom-example-utils

Dcom example utils

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscores or dashes in import statements.

Adding spaces inside the import statement.

Import statements use dot notation matching the package name.

3fill in blank

hard

Fix the error in the package declaration to follow Java syntax rules.

Java

package [1];

Drag options to blanks, or click blank then click option'

Acom.example.app

Bcom-example-app

Ccom_example_app

Dcom example app

Attempts:

3 left

💡 Hint

Common Mistakes

Using dashes or spaces in package names.

Using underscores instead of dots.

Package names must use dots to separate identifiers without spaces or dashes.

4fill in blank

hard

Fill both blanks to create a class Helper inside package org.tools.

Java

package [1];

public class [2] {
    // class content
}

Drag options to blanks, or click blank then click option'

Aorg.tools

BHelper

Chelper

Dorg_tools

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscores in package names.

Starting class names with lowercase letters.

Package names use dot notation; class names start with uppercase letters.

5fill in blank

hard

Fill all three blanks to declare package net.app.utils, import java.util.List, and define class DataHandler.

Java

package [1];

import [2];

public class [3] {
    // code here
}

Drag options to blanks, or click blank then click option'

Anet.app.utils

Bjava.util.List

CDataHandler

Dnet_app_utils

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscores in package or import names.

Incorrect capitalization of class names.

Package and import use dot notation; class names start with uppercase letters.

Practice

1. What is the main purpose of using packages in Java?

easy

A. To group related classes and organize code

B. To execute Java programs faster

C. To create graphical user interfaces

D. To store variables globally

Solution

1. Step 1: Understand what packages do

   Packages help organize classes by grouping related ones together.

2. Step 2: Identify the correct purpose

   Grouping related classes improves code organization and readability.

3. Final Answer:

   To group related classes and organize code -> Option A

4. Quick Check:

   Packages organize code = D [OK]

Hint: Packages group classes logically for better organization [OK]

Common Mistakes:

• Thinking packages speed up program execution
• Confusing packages with GUI creation
• Assuming packages store variables globally

2. Which of the following is the correct way to declare a package named com.example.app in a Java file?

easy

A. package com_example_app;

B. Package com.example.app;

C. package com.example.app;

D. import com.example.app;

Solution

1. Step 1: Check package declaration syntax

   The package statement must be lowercase and end with a semicolon.

2. Step 2: Match the correct syntax

   package com.example.app; uses correct lowercase 'package' keyword and dot notation with semicolon.

3. Final Answer:

   package com.example.app; -> Option C

4. Quick Check:

   Correct package syntax = C [OK]

Hint: Use lowercase 'package' and end with semicolon [OK]

Common Mistakes:

• Capitalizing 'Package' keyword
• Using underscores instead of dots
• Using 'import' instead of 'package'

3. Given the following Java file content, what will be the package of the class MyClass?

package org.test.project;

public class MyClass {
    public void display() {
        System.out.println("Hello from MyClass");
    }
}

medium

A. org.test.project

B. org.test

C. project

D. default package

Solution

1. Step 1: Read the package declaration

   The first line declares the package as 'org.test.project'.

2. Step 2: Identify the package of MyClass

   Since MyClass is declared after the package statement, it belongs to 'org.test.project'.

3. Final Answer:

   org.test.project -> Option A

4. Quick Check:

   Package line matches class package = B [OK]

Hint: Class package matches the declared package line [OK]

Common Mistakes:

• Assuming partial package names
• Thinking class is in default package without declaration
• Confusing package with folder names

4. Identify the error in the following Java file related to package declaration:

package MyApp.Utilities;

public class Helper {
    // class code
}

medium

A. Missing semicolon after package statement

B. Package name should be lowercase

C. Class name should be lowercase

D. Package keyword should be capitalized

Solution

1. Step 1: Check package naming conventions

   Package names should be all lowercase letters separated by dots.

2. Step 2: Identify the error

   'MyApp.Utilities' uses uppercase letters, which is against convention.

3. Final Answer:

   Package name should be lowercase -> Option B

4. Quick Check:

   Package names lowercase = A [OK]

Hint: Package names must be lowercase letters only [OK]

Common Mistakes:

• Using uppercase letters in package names
• Forgetting semicolon after package
• Capitalizing 'package' keyword

5. You want to create a package structure for a company named "TechCorp" with a project "Inventory" and a module "Reports". Which is the best package declaration for a Java class in the Reports module?

hard

A. package techcorp_inventory_reports;

B. package TechCorp.Inventory.Reports;

C. package tech_corp.inventory.reports;

D. package techcorp.inventory.reports;

Solution

1. Step 1: Follow Java package naming conventions

   Package names should be lowercase and use dots to separate levels.

2. Step 2: Evaluate options

   package techcorp.inventory.reports; uses all lowercase and dot notation correctly. Others use uppercase or underscores incorrectly.

3. Final Answer:

   package techcorp.inventory.reports; -> Option D

4. Quick Check:

   Lowercase with dots = A [OK]

Hint: Use lowercase names separated by dots for packages [OK]

Common Mistakes:

• Using uppercase letters in package names
• Using underscores instead of dots
• Combining all names without dots