String source = "This is a test string used to test wrap()";
int size = source.length();
CharBuffer c = CharBuffer.wrap(source,10,size);
System.out.println("Position :"+c.position()+" Expected : 10");

results in
Position :0 Expected : 10

because according to Specs
wrap(String str,int start,int end) wraps a string into a Buffer and its position will be start.