Ch 8: Strings Flashcards
in java, what is a string of characters represented by
an object of the String type
characteristics of String objects are
have methods
can be passed to other methods (always as references) or returned from methods
literal strings are
represented by text in double quotes ex: “Twitter”
what operators can be used to concatenate a string with another string, number , or an object
+ and +=
what is concatenation
combining of two strings with + or +=
what are escape characters
\ is used as the escape character ex: \n, \t, ", \
can a literal string be empty
yes, it is called an empty string ex: String s = “”;
do literal strings objects need to be created
even though they act as string object, they do not have to be created
explain String city = “Boston”;
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
the String class has over a dozen constructors, true or false
true, but it is less common to use constructors for strings than for other types of objects
is there a difference between String str = “Foo Fighters”; and String str = new String(“Foo Fighters”);
yes, but a far as your programmed is concerned, the two declarations act identically
what is the field of the String type set as default
private String Hello;
null
explain String s1 = “”;
s1 is set to an empty string
explain String s2 = new String();
s2 is set to an empty string
what happens when a method is called for a reference that is equal to null
program throws a NullPointerException and quits
once a string object is constructed, it cannot be changed. t or f
t
define immutable object
none of its methods can change the content of a String object
what type of object is a string
immutable object
what method allows you to get the value of a character at a given position in the string
charAt();
how do you set or replace a single character in a string
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"
what happens when there are no variables referring to an old string
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
explain String s2 = s1;
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
s2 = new String(s1);
two variables refer to different String objects with the same contents. this is copying a reference
