What is Java - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print "Hello, Java!" to the console.

Java

public class Main {
    public static void main(String[] args) {
        System.out.[1]("Hello, Java!");
    }
}

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

Aecho

Bprint

Cwrite

Dprintln

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'print' will print text but not move to a new line.

Using 'write' or 'echo' are not valid methods here.

The println method prints the text and moves to a new line.

2fill in blank

medium

Complete the code to declare an integer variable named 'age' with value 25.

Java

public class Main {
    public static void main(String[] args) {
        [1] age = 25;
    }
}

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

Aint

Binteger

Cvar

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'integer' is not a Java keyword.

Using 'var' requires Java 10+, but 'int' is standard.

In Java, int is the keyword to declare an integer variable.

3fill in blank

hard

Fix the error in the code to correctly create a Java class named 'Car'.

Java

public [1] Car {
    // class body
}

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

Aclass

Bmethod

Cfunction

Dinterface

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'function' or 'method' instead of 'class'.

Using 'interface' defines a different structure.

Use the keyword class to define a class in Java.

4fill in blank

hard

Fill both blanks to declare a method named 'greet' that returns nothing and prints a message.

Java

public [1] greet() {
    System.out.[2]("Hello!");
}

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

Avoid

Bprintln

Cprint

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'int' as return type when method returns nothing.

Using 'print' instead of 'println' for new line.

The method returns void (nothing) and uses println to print with a new line.

5fill in blank

hard

Fill all three blanks to declare a Java class 'Person' with a private String field 'name' and a constructor.

Java

public class Person {
    private [1] [2];

    public Person([1] [2]) {
        this.[2] = [2];
    }
}

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

Aint

BString

Cname

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'int' or 'age' instead of 'String' and 'name'.

Mismatching field and parameter names.

The field is a String named name. The constructor uses the same type and name.

Practice

1. What is Java primarily used for?

easy

A. Writing programs that can run on many devices

B. Designing websites with HTML and CSS

C. Creating spreadsheets and documents

D. Managing databases with SQL

Solution

1. Step 1: Understand Java's purpose

   Java is a programming language designed to write software that works on different devices.

2. Step 2: Compare with other options

   Options A, B, and D relate to other technologies, not Java's main use.

3. Final Answer:

   Writing programs that can run on many devices -> Option A

4. Quick Check:

   Java = cross-device programming language [OK]

Hint: Java runs programs on many devices, not just one [OK]

Common Mistakes:

• Confusing Java with web design languages
• Thinking Java is for document editing
• Mixing Java with database query languages

2. Which of the following is the correct way to start a Java program?

easy

A. def main():

B. function main() {}

C. public static void main(String[] args) {}

D. start() {}

Solution

1. Step 1: Identify Java's main method syntax

   Java programs start with the method: public static void main(String[] args) {}.

2. Step 2: Recognize other languages' syntax

   Options B, C, and D are syntax from JavaScript, Python, or invalid.

3. Final Answer:

   public static void main(String[] args) {} -> Option C

4. Quick Check:

   Java main method = public static void main(String[] args) [OK]

Hint: Java main method always uses 'public static void main(String[] args)' [OK]

Common Mistakes:

• Using Python or JavaScript syntax instead
• Omitting 'static' or 'public' keywords
• Writing main without parameters

3. What will the following Java code print?

public class Test {
  public static void main(String[] args) {
    System.out.println("Hello, Java!");
  }
}

medium

A. Hello Java

B. Hello, Java!

C. System.out.println("Hello, Java!");

D. Error: main method missing

Solution

1. Step 1: Read the code output statement

   The code calls System.out.println with the string "Hello, Java!" which prints exactly that.

2. Step 2: Confirm no syntax errors

   The main method and class are correctly defined, so it runs without error.

3. Final Answer:

   Hello, Java! -> Option B

4. Quick Check:

   Print statement outputs string exactly [OK]

Hint: System.out.println prints exactly the text inside quotes [OK]

Common Mistakes:

• Ignoring punctuation in output
• Confusing code with output
• Assuming missing main method error

4. Identify the error in this Java program:

public class Sample {
  public static void main(String args) {
    System.out.println("Test");
  }
}

medium

A. System.out.println is misspelled

B. Missing semicolon after println

C. Class name should be lowercase

D. Missing square brackets [] in main method parameter

Solution

1. Step 1: Check main method parameter

   The main method must have String[] args, but here it is String args without brackets.

2. Step 2: Verify other parts

   Semicolon is present, class name capitalization is allowed, and println is spelled correctly.

3. Final Answer:

   Missing square brackets [] in main method parameter -> Option D

4. Quick Check:

   Main method parameter must be String[] args [OK]

Hint: Main method parameter needs brackets: String[] args [OK]

Common Mistakes:

• Omitting [] in main method parameter
• Thinking class name must be lowercase
• Assuming missing semicolon error

5. You want to write a Java program that can run on any device without changes. Which feature of Java makes this possible?

hard

A. Java programs are compiled into bytecode run by the JVM

B. Java programs are interpreted directly from source code

C. Java programs require device-specific compilation

D. Java programs use HTML for compatibility

Solution

1. Step 1: Understand Java compilation

   Java code is compiled into bytecode, which is not tied to any device.

2. Step 2: Role of JVM

   The JVM (Java Virtual Machine) runs this bytecode on any device, enabling portability.

3. Final Answer:

   Java programs are compiled into bytecode run by the JVM -> Option A

4. Quick Check:

   Bytecode + JVM = cross-device Java programs [OK]

Hint: Java bytecode runs on JVM anywhere, no device changes needed [OK]

Common Mistakes:

• Thinking Java runs source code directly
• Assuming device-specific compilation is needed
• Confusing Java with web languages like HTML