@NotNull, @NotBlank, @NotEmpty in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to ensure the 'name' field cannot be null.

Spring Boot

public class User {
    @[1]
    private String name;
}

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

ANotEmpty

BNotBlank

CNotNull

DSize

Attempts:

3 left

💡 Hint

Common Mistakes

Using @NotBlank instead of @NotNull when only null check is needed.

Confusing @NotEmpty with @NotNull.

The @NotNull annotation ensures the field is not null but allows empty strings.

2fill in blank

medium

Complete the code to ensure the 'username' field is not null and not empty (no blank spaces).

Spring Boot

public class Account {
    @[1]
    private String username;
}

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

ANotEmpty

BNotNull

CSize(min=1)

DNotBlank

Attempts:

3 left

💡 Hint

Common Mistakes

Using @NotEmpty which allows strings with only spaces.

Using @NotNull which allows empty strings.

The @NotBlank annotation ensures the string is not null, not empty, and not just whitespace.

3fill in blank

hard

Fix the error in the code to ensure the 'tags' list is not null and contains at least one element.

Spring Boot

public class BlogPost {
    @[1]
    private List<String> tags;
}

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

ANotEmpty

BNotBlank

CNotNull

DSize(min=1)

Attempts:

3 left

💡 Hint

Common Mistakes

Using @NotBlank on a collection causes errors.

Using @NotNull allows empty collections.

The @NotEmpty annotation ensures the collection is not null and has at least one element.

4fill in blank

hard

Fill both blanks to validate 'email' so it is not null and not blank.

Spring Boot

public class Contact {
    @[1]
    @[2]
    private String email;
}

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

ANotNull

BNotBlank

CNotEmpty

DEmail

Attempts:

3 left

💡 Hint

Common Mistakes

Using only @NotNull allows blank strings.

Using only @NotEmpty does not check for blank spaces.

Using both @NotNull and @NotBlank ensures the email is not null and not blank. However, @NotBlank alone is enough for strings, but sometimes both are used for clarity.

5fill in blank

hard

Fill all three blanks to create a map of word lengths for words longer than 3 characters.

Spring Boot

Map<String, Integer> wordLengths = words.stream()
    .filter(word -> word.length() [1] 3)
    .collect(Collectors.toMap(
        word -> word.[2](),
        word -> word.[3]()
    ));

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

A>

BtoUpperCase

Clength

DstartsWith

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > in filter.

Using startsWith instead of toUpperCase for keys.

Using toUpperCase instead of length for values.

The filter uses > to select words longer than 3. The key is the uppercase word using toUpperCase(), and the value is the word length using length().