Scenario: You need to convert a String to an int in your application. What are the different ways to do this, and which one would you prefer?

Detailed Answer:

In Java, there are two common methods to convert a String to an integer:

• Integer.parseInt(String):
  • This method converts a String to a primitive int.
  • It is lightweight and efficient because it directly returns a primitive value.
  • Example:
    String str = "123";
    int primitiveInt = Integer.parseInt(str); // Returns primitive int
    

• Integer.valueOf(String):
  • This method converts a String to an Integer object (wrapper class).
  • It is useful when you need an Integer object instead of a primitive int.
  • It also leverages the Integer cache for values between -128 and 127, which can improve performance and memory usage.
  • Example:
    String str = "123";
    Integer wrapperInt = Integer.valueOf(str); // Returns Integer object

Why Use valueOf() for Wrapper Classes and parseInt() for Primitives?

1. Integer.parseInt():
   • Use this when you need a primitive int.
   • It is faster and more memory-efficient because it avoids creating an additional Integer object.
   • Example use case: When performing arithmetic operations or storing values in primitive arrays.
2. Integer.valueOf():
   • Use this when you need an Integer object.
   • It is useful when working with collections (e.g., ArrayList<Integer>) or APIs that require objects.
   • It also benefits from the Integer cache, which reuses Integer objects for small values (-128 to 127), reducing memory overhead.
   • Example use case: When storing values in collections or passing them to methods that expect objects.