Java Programming - Objects and Collections
- Objects and Collections - General Questions
- Objects and Collections - Finding the output
- Objects and Collections - Pointing out the correct statements
An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value.
LinkedHashMap is the collection class used for caching purposes. FIFO is another way to indicate caching behavior. To retrieve LinkedHashMap elements in cached order, use the values() method and iterate over the resultant collection.
Hashtable is the only class listed that provides synchronized methods. If you need synchronization great; otherwise, use HashMap, it's faster.
Option A is valid declaration of float.
Option B is incorrect because any literal number with a decimal point u declare the computer will implicitly cast to double unless you include "F or f"
Option C is incorrect because it is a String.
Option D is incorrect because "d" tells the computer it is a double so therefore you are trying to put a double value into a float variable i.e there might be a loss of precision.
/* Missing Statement ? */
public class foo
{
public static void main(String[]args)throws Exception
{
java.io.PrintWriter out = new java.io.PrintWriter();
new java.io.OutputStreamWriter(System.out,true);
out.println("Hello");
}
}
The usual method for using/importing the java packages/classes is by using an import statement at the top of your code. However it is possible to explicitly import the specific class that you want to use as you use it which is shown in the code above. The disadvantage of this however is that every time you create a new object you will have to use the class path in the case "java.io" then the class name in the long run leading to a lot more typing.