Ch 8: Strings

Question 1

in java, what is a string of characters represented by

Answer 1

an object of the String type

Question 2

characteristics of String objects are

Answer 2

have methods

can be passed to other methods (always as references) or returned from methods

Question 3

literal strings are

Answer 3

represented by text in double quotes ex: “Twitter”

Question 4

what operators can be used to concatenate a string with another string, number , or an object

Answer 4

+ and +=

Question 5

what is concatenation

Answer 5

combining of two strings with + or +=

Question 6

what are escape characters

Answer 6

\ is used as the escape character ex: \n, \t, ", \

Question 7

can a literal string be empty

Answer 7

yes, it is called an empty string ex: String s = “”;

Question 8

do literal strings objects need to be created

Answer 8

even though they act as string object, they do not have to be created

Question 9

explain String city = “Boston”;

Answer 9

sets the reference city to a String object “Boston”. Boston is not the name of the variable (its name is city). Boston is its value

Question 10

the String class has over a dozen constructors, true or false

Answer 10

true, but it is less common to use constructors for strings than for other types of objects

Question 11

is there a difference between String str = “Foo Fighters”; and String str = new String(“Foo Fighters”);

Answer 11

yes, but a far as your programmed is concerned, the two declarations act identically

Question 12

what is the field of the String type set as default

private String Hello;

Answer 12

null

Question 13

explain String s1 = “”;

Answer 13

s1 is set to an empty string

Question 14

explain String s2 = new String();

Answer 14

s2 is set to an empty string

Question 15

what happens when a method is called for a reference that is equal to null

Answer 15

program throws a NullPointerException and quits

Question 16

once a string object is constructed, it cannot be changed. t or f

Answer 16

t

Question 17

define immutable object

Answer 17

none of its methods can change the content of a String object

Question 18

what type of object is a string

Answer 18

immutable object

Question 19

what method allows you to get the value of a character at a given position in the string

Answer 19

charAt();

Question 20

how do you set or replace a single character in a string

Answer 20

String bandName = “Foo Fighters”;
char c = bandName.charAt(0);
bandName = Character.toLowerCase(c) + bandName.substring(1);

// bandName now refers to a new string
// with the value "foo fighters"

Question 21

what happens when there are no variables referring to an old string

Answer 21

the old string is “thrown away” due to java’s automatic garbage collector releases the memory from the old string and returns it to the free memory pool

Question 22

explain String s2 = s1;

Answer 22

two variables refer to the same string object. ex= s1 and s2 both point to one String object of “Foo Fighters”
this is assigning a reference

Question 23

s2 = new String(s1);

Answer 23

two variables refer to different String objects with the same contents. this is copying a reference