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What's a Generic Class?
It's a class with one or more type variables. Here's a simple
example:
package examples;
/**
* A simple class to represent a pair of values
* of potentially different types.
*
*/
public class Pair<T1, T2>
{
/**
* Creates a new instance of Pair
*/
public Pair(T1 first, T2 second)
{
m_first = first;
m_second = second;
}
public T1 getFirst()
{
return m_first;
}
public void setFirst(T1 value)
{
m_first = value;
}
public T2 getSecond()
{
return m_second;
}
public void setSecond(T2 value)
{
m_second = value;
}
private T1 m_first;
private T2 m_second;
}
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and here's a very simple class to test it out:
package examples;
public class PairTest
{
public static void main(String[] args)
{
Pair<String, Integer> pair1 =
new Pair<String, Integer>("Fred Bloggs", 5);
System.out.println( pair1.getFirst() + " owns " + pair1.getSecond() );
}
}
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This outputs:
Fred Bloggs owns 5
I could have chosen any combination of types (other than primitive types) for
my purposes.
In other words, I am able to write a generally useful class and parameterize
it with types. Then, I can specify the types that I need when I come to
use that class.
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