Java Reference Methods

Question 1

equals method

Answer 1

defined in object, takes in an object and compares is

Question 2

“hello”.substring( 3)

Answer 2

gives “lo” as h is zero, e is 1, and so on until the second l is 3.

Question 3

“A”.compareTo(“B”)

“A”.compareTo(“a”)

Answer 3

both are negative, a before b, and capitals before lowercase.

Question 4

Replace an element in an array list

Answer 4

ArrayList: E set(index, E value)
returns the value being replaced
ArrayList list = new ArrayList();
list.add("Hello");
String hello = list.set(0, "Goodbye");

Question 5

ArrayList numlist = new ArrayList();
list.add("Hello");

Does this give you a) no error, b) a compile time error c) a runtime error?

Answer 5

Compile time error.

Question 6

ArrayList untyped = new ArrayList()
untyped.add(new Integer(1));
untyped.add("Hello");
ArrayList stringList = (ArrayList)untyped;
String firstString = stringList.get(0);

Does this give you a) no error, b) a compile time error c) a runtime error?

Answer 6

runtime error