chapter 5

Question 1

What is string concatentation?

Answer 1

Placing one string before the other and combining them.

Question 2

What are the two ways the ways the + can be interpreted?

Answer 2

1. If both operands are numeric, + means numeric addition.

2. If either operand is a String, + means concatenation.

Question 3

What is an immutable object?

Answer 3

An object that cannot be changed once it is created.

Question 4

Is the String type immutable?

Answer 4

yes.

Question 5

What does String.length() return?

Answer 5

The number of characters in String.

Question 6

What does String.charAt(1) return?

Answer 6

The char value at index 1 or throws IndexOutOfBoundsException - if the index argument is negative or not less than the length of this string.

Question 7

What does String.indexOf() do?

Answer 7

Returns the index within this string of the first occurrence of the specified value, or -1.

Question 8

What are the method signatures for indexOf()?

Answer 8

int indexOf(int ch)
int indexOf(int ch, int fromIndex)
int indexOf(String str)
int indexOf(String str, int fromIndex)

Question 9

What does the String.substring(int beginIndex) do?

Answer 9

Returns a new string that is a substring of this string. `

Question 10

What are the method signatures for substring()?

Answer 10

String substring(int beginIndex)
String substring(int beginIndex, int endIndex)

Question 11

Is the value at the endIndex in the substring() included ?

Answer 11

No.

Question 12

What does toLowerCase() and toUpperCase() do?

Answer 12

toLowerCase(): converts any uppercase characters to lowercase in the returned string.
toUpperCase(): converts any lowercase characters to uppercase in the returned string.

Question 13

What does the String.equals() method do?

Answer 13

Returns true if the given object represents a String equivalent to this string, false otherwise.

Question 14

What does the String.equalsIgnoreCase() do?

Answer 14

Returns true if the argument is not null and it represents an equivalent String ignoring case; false otherwise.

Question 15

What does the startsWith() do?

Answer 15

boolean startsWith(String prefix): Returns true if the character sequence represented by the argument is a prefix of the character sequence represented by this string; false otherwise. Note also that true will be returned if the argument is an empty string or is equal to this String object as determined by the equals(Object) method.

Question 16

What does the endsWith() do?

Answer 16

boolean endsWith(String suffix): Returns true if the character sequence represented by the argument is a suffix of the character sequence represented by this object; false otherwise. Note that the result will be true if the argument is the empty string or is equal to this String object as determined by the equals(Object) method.

Question 17

What does the String.replace() do?

Answer 17

Replaces some value(s) with different value(s).

Question 18

What are the two method signatures for replace()?

Answer 18

replace(char oldChar, char newChar)

replace(CharSequence target, CharSequence replacement)

Question 19

What does the String.contains() do?

Answer 19

Returns true if and only if this string contains the specified sequence of char values.

Question 20

What do the trim(), strip(), stripLeading(), and stripTrailing() methods do?

Answer 20

Remove whitespace from the beginning, ending or both ends of the string.

Question 21

What is the difference between strip() and trim()?

Answer 21

strip() supports Unicode.

Question 22

What does the String.intern() do?

Answer 22

Returns a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.

Question 23

What is the StringBuilder class?

Answer 23

A class to create mutable strings.

Question 24

What are four common StringBuilder methods?

Answer 24

charAt(), indexOf(), length(), and substring().

Question 25

What does the StringBuilder.append() do?

Answer 25

Appends the string representation of the argument to this sequence and returns a reference to this StringBuilder.

Question 26

What does the StringBuilder.insert() do?

Answer 26

Adds characters to the StringBuilder as the requested index and returns a reference to this StringBuilder.

Question 27

What does StringBuilder.delete(int start, int end) do?

Answer 27

Removes the characters in a substring of this sequence. The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists. If start is equal to end, no changes are made. Throws StringIndexOutOfBoundsException - if start is negative, greater than length(), or greater than end.

Question 28

What does StringBuilder.deleteCharAt(int index) do?

Answer 28

Removes the char at the specified position in this sequence. Throws StringIndexOutOfBoundsException - if the index is negative or greater than or equal to length().

Question 29

What does StringBuilder.replace(int start,
int end,
String str) do?

Answer 29

Replaces the characters in a substring of this sequence with characters in the specified String. The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists. First the characters in the substring are removed and then the specified String is inserted at start. Throws StringIndexOutOfBoundsException - if start is negative, greater than length(), or greater than end.

Question 30

What does StringBuilder.reverse() do?

Answer 30

Causes this character sequence to be replaced by the reverse of the sequence and returns a reference to this object.

Question 31

What type of compilation error is thrown if you try to compare two different object types using ==?

Answer 31

incompatible types error.

Question 32

What is the string pool in Java?

Answer 32

The Java string constant pool is an area in heap memory where Java stores literal string values. The heap is an area of memory used for run-time operations. However, if you create a new instance of a String object, it will create a new string literal in the pool, even if one already exists.

Question 33

What does the String.intern() do?

Answer 33

Returns a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.

Question 34

What is the basic structure of an array?

Answer 34

int[] number = new int[3];

int = type of array
[] Array symbol (required)
3 = size of the array

Question 35

What is an example of an anonymous array?

Answer 35

int[] numbers = {1,2,3};

Its anonymous because the type and size were not specified.

Question 36

Where can the [] go when defining an array?

Answer 36

Before or after the name.

Question 37

What types of variables result from:

int ids[], types;

Answer 37

A variable named ids of type int[]

A variable named types of type int

Question 38

What method does Java have to print arrays nicely?

Answer 38

Arrays.toString(someArray);