1. make your class final, so that no other class can be inherited
2. Make sure that all variables are final and private.
3. No setter methods.
4. Provide a constructor which can take values to these variables.
Example:
final class MyImmutableClass
{
// instance var are made private & final to restrict the access
private final int count;
private final double value;
// Constructor where we can provide the constant value
public MyImmutableClass(int paramCount,double paramValue)
{
count = paramCount;
value = paramValue;
}
// provide only methods which return the instance var
// & not change the values
public int getCount()
{
return count;
}
public double getValue()
{
return value;
}
}
// class TestImmutable
public class TestImmutable
{
public static void main(String[] args)
{
MyImmutableClass obj1 = new MyImmutableClass(3,5);
System.out.println(obj1.getCount());
System.out.println(obj1.getValue());
// there is no way to change the values of count & value-
// no method to call besides getXX, no subclassing, no public access to var -> Immutable
}
}
