User-defined functions (UDFs) in Hadoop - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple UDF that returns the length of a string.

Hadoop

public class StringLengthUDF extends UDF {
    public int evaluate(String input) {
        return input[1];
    }
}

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

A.length()

B.size()

C.count()

D.length

Attempts:

3 left

💡 Hint

Common Mistakes

Using .length without parentheses, which is a property in arrays but not in String.

Using .size() or .count(), which are not valid String methods.

The correct method to get the length of a string in Java is .length() with parentheses.

2fill in blank

medium

Complete the code to register the UDF in Hive using the correct syntax.

Hadoop

CREATE TEMPORARY FUNCTION string_len AS '[1]';

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

Astring_len

BStringLengthUDF

Ccom.example.StringLengthUDF

Dcom.example.udf.StringLength

Attempts:

3 left

💡 Hint

Common Mistakes

Using only the class name without package.

Using the function name instead of the class path.

The full class path including package is needed to register the UDF in Hive.

3fill in blank

hard

Fix the error in the UDF evaluate method to handle null input safely.

Hadoop

public Integer evaluate(String input) {
    if (input == null) {
        return [1];
    }
    return input.length();
}

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

Anull

B0

C-1

Dthrow new IllegalArgumentException()

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 0 or -1 which may be misleading as length.

Throwing an exception which breaks query execution.

Returning null for null input is a common safe practice in UDFs to avoid errors.

4fill in blank

hard

Fill both blanks to create a UDF that converts input string to uppercase safely.

Hadoop

public class ToUpperUDF extends UDF {
    public String evaluate(String input) {
        if (input == null) {
            return [1];
        }
        return input[2];
    }
}

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

Anull

B""

C.toUpperCase()

D.toLowerCase()

Attempts:

3 left

💡 Hint

Common Mistakes

Returning empty string instead of null.

Using .toLowerCase() instead of .toUpperCase().

Return null if input is null, and use .toUpperCase() to convert string to uppercase.

5fill in blank

hard

Fill all three blanks to create a UDF that returns the first character of a string or null if empty.

Hadoop

public class FirstCharUDF extends UDF {
    public String evaluate(String input) {
        if (input == null || input[1] 0) {
            return [2];
        }
        return input[3];
    }
}

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

A.length() <=

Bnull

C.substring(0, 1)

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using == 0 instead of .length() <= 0.

Returning empty string instead of null.

Using substring with wrong indexes.

Check if length is 0 or less, return null, else return substring of first character.