Wrapper classes for primitive types:
Primitive type | Wrapper class |
byte | Byte |
short | Short |
int | Interger |
long | Long |
float | Float |
double | Double |
char | Char |
boolean | Boolean |
Example 1: Code that adds integers to an untyped array list:
ArrayList number = new ArrayList(); nubers.add(new Integer(1)); nubers.add(new Integer(2)); nubers.add(new Integer(3));
Example 2: Code that retrieves intergers from the array list:
for (int i = 0; numbers.size(); i++) { int number = (Integer)numbers.get(i); System.out.pringln(number); }
Description:
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Because untyped collections hold elements of thpe Object, they can't hold primitive types. As a result you must use wrapper claases to store primitive types in a collection.
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To add a primitive type to an untyped collectio, create an instance of the appropriate wrapper class and pass the value you want it to hold to the construtor of that class.
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To retrieve an element that holds a primitive type, cast the element to the wrapper type.