Data
Working with data types
Integer and Double classs
How to use the Integer and Double classes
- The Integer and Double classes are known as wrapper classes since they can be used to construct Integer and Double objects that contain (wrap around) int and double values.
- These classes can be useful when you need to pass an int or double value to a method that accepts only objects, not primitive data types.
- These classes also provide static methods that you can use for converting values from these data types to strings and vice versa.
- If the parseInt and parseDouble methods can't successfully parse the string, they will cause an error to occur. In Java terminology, this is known as throwing an exception.
- Every primitive type has a wrapper class that works like the Integer and Double classes.
Constructors for the Integer and Double classes
| Constructor | Description |
|---|---|
| Integer(int) | Constructs an Integer object from an int data type. |
| Double(double) | Constructs a Double object from a double data type. |
Two static methods of the Integer class
| Method | Description |
|---|---|
| parseInt(stringName) | Attempts to convert the String object that's supplied as an argument to an int type. If successful, it returns the int value. If unsuccessful, it throws an exception. |
| toString(intName) | Converts the int value that's supplied as an argument to a String object and returns that String object. |
Two static methods of the Double class
| Method | Description |
|---|---|
| parseDouble(stringName) | Attempts to convert the String object that's supplied as an argument to a double type. If successful, it returns the double value. If unsuccessful, it throws an exception. |
| toString(doubleName) | Converts the double value that's supplied as an argument to a String object and returns that String object. |
How to create Integer and Double objects
Integer quantityDoubleObject = new Integer(quantity);Double priceDoubleObject = new Double(price);
How to use static methods to convert primitive types to String objects
String counterString = Integer.toString(counter);String priceString = Double.toString(price);
How to use static methods to convert String objects to primitive types
int quantity = Integer.parseInt(quantityString);double price = Double.parseDouble(priceString);