Wrapper Classes - Parse & ValueOf

parse methods are more commonly used for parsing simple primitive values from strings.

valueOf methods are useful when

• you need to handle cases where the input can be null or
• when you want to work with wrapper objects.

Difference between parse and valueOf Methods

Both parse and valueOf methods are used to convert Strings (textual representations) of primitive data types or objects into their respective Java types.

However, there are some differences between the two methods:

1. Usage:
   • parse methods are usually static methods defined in primitive wrapper classes (Integer, Double, etc.) and the java.time classes for parsing date and time formats.
   • valueOf methods are usually static methods defined in primitive wrapper classes (Integer, Double, etc.), and they return the respective wrapper object. They are also present in some other classes like Boolean, BigInteger, and BigDecimal.
2. Return Type:
   • parse methods return the primitive data type corresponding to the parsed value. For example, Integer.parseInt(String) returns an int.
   • valueOf methods return an instance of the corresponding wrapper class. For example, Integer.valueOf(String) returns an Integer.
3. Exception Handling:
   • parse methods may throw a NumberFormatException if the provided string cannot be parsed as the respective primitive type.
   • valueOf methods can return null if the provided string cannot be parsed, but they generally don’t throw exceptions.
4. Null Handling:
   • parse methods do not handle null values; passing null to parse methods will result in a NullPointerException.
   • valueOf methods can handle null by returning null.
5. Usages:
   • parse methods are commonly used when you expect valid input and want the parsed primitive value directly. For example, Integer.parseInt("123") returns an int.
   • valueOf methods are often used when you want to handle possible null values or if you need to manipulate the parsed value further. For example, Integer.valueOf("123") returns an Integer, which can be assigned to an Integer reference and can handle null values.

Using parse:

int intValue = Integer.parseInt("123");
double doubleValue = Double.parseDouble("3.14");

Using valueOf:

Integer integerObject = Integer.valueOf("123");
Double doubleObject = Double.valueOf("3.14");
Boolean booleanObject = Boolean.valueOf("true");