Class XII IP Java Flow of Control Questions

1. what is the output of the following java statement
int x=10;
System.out.println(""+ ++x);

2. what is the output of the following

int i=0;
while(i<10)
{
       System.out.println(""+i);
       i++;
       if(i%3==0)
            System.out.println("---");
}

3. What are the main two difference betweem If else and switch case

4. What is the difference  between double and Float datatype in java

5. what is a NULL datatype.