Best practices in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a constant for the maximum number of users.

Java

public class Config {
    public static final int MAX_USERS = [1];
}

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Afinal

B"100"

CmaxUsers

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around numbers which makes them strings.

Trying to use variable names instead of values.

Constants in Java are declared using public static final and assigned a fixed value like 100.

2fill in blank

medium

Complete the method to override the toString method properly.

Java

public class Person {
    private String name;
    @Override
    public String toString() {
        return [1];
    }
}

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A"Person: " + name

Bname

Cname.toString()

Dsuper.toString()

Attempts:

3 left

💡 Hint

Common Mistakes

Returning just the variable without context.

Calling toString() on a String variable unnecessarily.

Overriding toString() should return a meaningful string, like "Person: " plus the name.

3fill in blank

hard

Fix the error in the method to properly close the resource using try-with-resources.

Java

public void readFile(String path) {
    try (BufferedReader reader = new BufferedReader(new FileReader([1]))) {
        System.out.println(reader.readLine());
    } catch (IOException e) {
        e.printStackTrace();
    }
}

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AfilePath

B"path"

Cpath

Dreader

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string literal instead of the variable.

Using an undefined variable name.

The variable path is passed as the filename to FileReader. Using the string "path" would look for a file literally named 'path'.

4fill in blank

hard

Fill both blanks to create a for-each loop that prints each element in the list.

Java

List<String> items = List.of("apple", "banana", "cherry");
for ([1] : [2]) {
    System.out.println(item);
}

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AString item

Bitems

Cint i

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using an index variable instead of the element variable.

Using the wrong collection variable name.

A for-each loop uses the syntax: for (Type variable : collection). Here, String item and items are correct.

5fill in blank

hard

Fill all three blanks to create a map comprehension that filters and transforms entries.

Java

Map<String, Integer> result = data.entrySet().stream()
    .filter(e -> e.getValue() [1] [2])
    .collect(Collectors.toMap(
        e -> e.getKey().toUpperCase(),
        e -> e.getValue() [3] 2
    ));

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A>

B10

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong comparison operator.

Using addition instead of multiplication for transformation.

This code filters entries with values greater than 10, then collects them into a map with uppercase keys and values multiplied by 2.