Safe Management of Multiple Resources

In this problem, you will create an executeQuery method that manages two AutoCloseable resources (DatabaseConnection and QueryExecutor) using try-with-resources, returns a result string for valid queries, and throws appropriate exceptions for invalid input.

Learning Objective: Understand how to manage multiple resources with try-with-resources while combining exception handling

Overview

The try-with-resources statement can declare multiple resources separated by semicolons, and they are automatically closed in reverse declaration order. This problem combines resource management with input validation.

Specifications

DatabaseConnection class (implements AutoCloseable)

• Constructor: no arguments
• close(): releases the resource

QueryExecutor class (implements AutoCloseable)

• Constructor: no arguments
• execute(String query) method:
  • If query is null, throws NullPointerException (message: "Query cannot be null")
  • If query is an empty string, throws IllegalArgumentException (message: "Query cannot be empty")
  • If valid, returns "Result: " + query

Main class

• Define static String executeQuery(String query) method
  • Declare both DatabaseConnection and QueryExecutor in try-with-resources
  • Return the result of executor.execute(query)

Examples

• executeQuery("SELECT * FROM users") → "Result: SELECT * FROM users"
• executeQuery(null) → NullPointerException: "Query cannot be null"
• executeQuery("") → IllegalArgumentException: "Query cannot be empty"