Chapter 4.4 Strings

Question 1

Define a string

Answer 1

A string is a sequence of characters.
A string value is enclosed in matching double quotes (“).

Question 2

Strings are known as a ___ type not an ___

Answer 2

The String type is not a primitive type. It is known as a reference type. Any Java class can be used as a reference type for a variable.

Question 3

Strings must be surrounded by ___

and they contain most characters except:

Answer 3

1. Must be surrounded double quotes.

String literals (values) have the quotation marks removed when displayed.

2. Strings can contain most characters except enter, backspace, tab, and backslash.

These characters must be escaped by using an escape sequence which consists of the escape character () followed by a character or a combination of digits.

Question 4

Strings can have up to ___ characters

Answer 4

Potentially up to 2,147,483,647 characters is allowed.

The minimum number of characters is zero “”, which is called the empty string.

Question 5

Backspace

Escape sequence:
Unicode:
Decimal value:

Answer 5

\b
\u0008
8

Question 6

Tab

Escape sequence:
Unicode:
Decimal value:

Answer 6

\t
\u0009
9

Question 7

Linefeed

Escape sequence:
Unicode:
Decimal value:

Answer 7

\n
\u000C
10

Question 8

Formfeed

Escape sequence:
Unicode:
Decimal value:

Answer 8

\f
\u000C
12

Question 9

Carriage return

Escape sequence:
Unicode:
Decimal value:

Answer 9

\r
\u000D
13

Question 10

Backlash

Escape sequence:
Unicode:
Decimal value:

Answer 10

\u005C
92

Question 11

Double quote:

Escape sequence:
Unicode:
Decimal value:

Answer 11

"
\u0022
34

Question 12

Syntax for a simple method for String objects

Answer 12

referenceVariable.methodName(arguments)

ex:
String message = “Welcome to Java”;
System.out.println(“The length of “ + message + “ is “ +message.length());

Question 13

What is the String method to return the number of characters in the String

Answer 13

length() or length() - 1

Question 14

What is the String method to return the character at the specified index from this string

Answer 14

charAt(index)

The charAt(index) method can be used to retrieve a specific character in a string s,
where the index is between 0 and length()–1.

Question 15

What is the String method to return a new String that concatenates

Answer 15

concat(s1)

Question 16

What is the String method to return a new string with all letters uppercase

What is the String method to return a new string with all letters lowercase

Answer 16

toUpperCase()
toLowerCase()

Question 17

What is the String method to return a new string with whitespace characters trimmed on both sides

Answer 17

trim()

Question 18

Java uses the + operator for both addition and concatenation.

Answer 18

If one of the operands is a nonstring (e.g., an integer), the nonstring value is converted into a string and concatenated with the other string.
If neither of the operands is a string, the plus sign (+) is the addition operator that adds two numbers.

Question 19

Reading a String from the console

Answer 19

To read a string from the console, invoke the next() method on a Scanner object.
The next() method reads a string that ends with a whitespace character.

Scanner input = new Scanner(System.in);
System.out.print(“Enter three words separated by spaces: “);
String s1 = input.next();
String s2 = input.next();
String s3 = input.next();
System.out.println(“s1 is “ + s1);
System.out.println(“s2 is “ + s2);
System.out.println(“s3 is “ + s3);

Question 20

You can use the ___ method to read an entire line of text.

Answer 20

You can use the nextLine() method to read an entire line of text. The nextLine() method reads a string that ends with the Enter key pressed.

Scanner input = new Scanner(System.in);
System.out.println(“Enter a line: “);
String s = input.nextLine();
System.out.println(“The line entered is “ + s);

Note:
To avoid input errors, be cautious using line-based input after a token-based input in thepro­gram.

Question 21

Comparing Strings: returns true if this String is equal to string s1

Answer 21

equals(s1)

Question 22

Comparing Strings: returns true if this string is equal to string s1

Answer 22

equalsIgnoreCase(s1)

Question 23

Return an integer greater than 0, equal to 0, or less than 0 to indicate whether this string is greater than, equal to, or less than s1

Answer 23

compareTo(s1)

Question 24

Same to compareTo except that the comparison is case sensitive

Answer 24

compareToIgnoreCase(s1)

Question 25

Returns true if this String starts with the specified prefix

Answer 25

startsWith(prefix)

Question 26

Returns true if this string ends with the specified suffix

Answer 26

endWith(suffix)

Question 27

Returns this substring that begins with the character at the specified beginIndex and extends to the end of the string

Answer 27

substring(beginindex)

Question 28

Returns this String’s substring that begins at the specified beginIndex and extends to the character at the endIndex is not part of the substring

Answer 28

substring(beginIndex, endIndex)

Question 29

Returns the index of the of the first occurrence of the ch in the string

Answer 29

indexOf(ch)

Question 30

Returns the index of the first occurrence of ch after fromIndex in the String, Returns -1 if not matched

Answer 30

indexOf(ch, fromIndex)

Question 31

Returns the index of the first occurrence of the of string s in the String. Returns -1 if not matched

Answer 31

indexOf(s)

Question 32

Returns the index of the first occurrence of String s in this string after fromIndex. Returns true if not matched.

Answer 32

indexOf(s, fromIndex)

Question 33

Returns the index of the last occurrence of ch in the String. Returns -1 if not matched.

Answer 33

lastIndexOf(ch)

Question 34

Returns the index of the last of the last occurrence of ch before fromIndex in this string. Return -1 if not matched.

Answer 34

lastIndexOf(ch, fromIndex)

Question 35

Return the index of the last occurrence of string s. Returns -1 if not matched.

Answer 35

lastIndexOf(s)

Question 36

Returns the index of the last occurrence of string s before fromIndex. Returns -1 if not matched.

Answer 36

lastIndexOf(s, fromIndex)

Question 37

To convert a string into an int value, use the ___ method:

Answer 37

To convert a string into an int value, use the Integer.parseInt method:

int intValue = Integer.parseInt(intString);

Question 38

To convert a string into a double value, use the ___ method:

Answer 38

To convert a string into a double value, use the Double.parseDouble method:

double doubleValue = Double.parseDouble(doubleString);

If the string is not a numeric string, conversion would cause a runtime error.

Question 39

To convert a number into a string use the string concatenating operator as follows:

Answer 39

To convert a number into a string use the string concatenating operator as follows:

String str = intValue + “ “ + doubleValue;

Question 40

Formatting output: how to display numbers in a certain format (Strings)

Answer 40

Often, it is desirable to display numbers in a certain format. To do that we can use the printf statement:

System.out.printf(format, items);

Where format is a string that may consist of substrings and format specifiers.

Question 41

What type does an item have to be to format output

Answer 41

1. An item may be a numeric value, character, boolean value, or a string.

Question 42

What does a format specifier specifier do

Answer 42

A format specifier specifies how an item should be displayed.

Question 43

How to format output

Answer 43

Each specifier begins with a percent sign (%).

To output a literal % in the format string, use %%

Items must match the format specifiers in order, in number, and in exact type.

You can specify the field width and precision in a format specifier.

By default, the output is right justified. You can put the minus sign (−) in the format specifier to specify that the item is left justified in the output within the specified field.

Question 44

%b output and example

Answer 44

boolean
T or F

Question 45

%c output and example

Answer 45

a character
‘a’

Question 46

%d output and example

Answer 46

a decimal integer
200

Question 47

%f output and example

Answer 47

a floating point number
45.46000

Question 48

%e output and example

Answer 48

a number in standard scientific notation
4.556000e+01

Question 49

format syntax

Answer 49

1.2f

1 = field width
2 = precision
f = conversion code

Question 50

Character method to: return the lowercase of the specified character

Answer 50

Math.pow(a, b)