Java Ch 4

Front 1

9 trig methods in the Math class

Back 1

Math.sin(radians)

cos(radians)

tan(radians)

asin(radians) //arcsin

acos(radians)

atan(radians)

toRadians(degrees)

toDegrees(radians)

Front 2

5 exponent methods in the Math class

Back 2

Math.exp(x); //returns e^x

log(x); //natural log of x

log10(x);

pow(a,b);

sqrt(x);

Front 3

4 rounding methods in Math class

Back 3

Math.ceil(x); //rounds up to nearest int. returned as double

Math.floor(x); //rounds down to nearest int. returned as double

rint(x); //rounds up to nearest int. if equally close, even is returned as double

round(x); // Returns (int)Math.floor(x + 0.5) if x is a float and returns (long)Math.floor(x + 0.5) if x is a double.

Front 4

Syntax for min and max methods

Back 4

Math.min(a,b);//returns min of these two

Math.max(a,b);

Front 5

Logic to use Math.random() to generate a random number between a and b, excluding b

Back 5

a + Math.random()*b

or a + (int)(Math.random())*b

Front 6

encoding

Back 6

mapping a character to its binary representation

Front 7

Unicode and ASCII are ________ ________

Back 7

encoding schemes

Front 8

True or false: Unicode is 8 bits. ASCII is 16 bits and includes unicode

Back 8

FALSE

Unicode is 16 bits and includes ASCII. ASCII is 8 bits

Front 9

Range for unicode

Back 9

\u0000 to \uFFFF

Front 10

How can you easily get the preceding or subsequent Unicode character?

Back 10

++ or --

Front 11

Is \a a special character in Java?

Back 11

no, but the others one I'm used to are

Front 12

true or false: a char can be cast into any numeric data type

Back 12

true! and the reverse is also true

Front 13

Will this casting work?

byte b = '\uFFF4';

byte b = 'a';

Back 13

no. It will not fit into one byte. it needs two bytes.

yes. that fits into a single byte

Front 14

What is the value of i?

int i = '2' + '3';

Back 14

i = 101;

'2' = 50

'3' = 51

Front 15

True or false: you can compare chars using relational operators

Back 15

true

Front 16

7 methods in Character class

Character.isDigit(ch);

Character.isLetter(ch);

isLetterOrDigit(ch);

isLowerCase(ch);

isUpperCase(ch);

toLowerCase(ch);

toUpperCase(ch);

Back 16

Character.isDigit(ch); //returns bool

Character.isLetter(ch);

isLetterOrDigit(ch);

isLowerCase(ch);

isUpperCase(ch);

toLowerCase(ch); //returns char

toUpperCase(ch);

Front 17

String is not a primitive type. It is a _____ type

Back 17

reference type

(the variable declared by a reference type references an object, which in this case is a string)

Front 18

6 simple methods for String OBJECTS

Back 18

length();

charAt(index);

concat(s1); //returns a new string that concatenates this string with s1

toUpperCase();

toLowerCase();

trim(); //trims whitspace on either side

Front 19

These simple methods from String objects can only be invoked from a specific String instance so they are called _______ methods as opposed to ______ methods

Back 19

instance

static

(Math uses static methods that don't require an object)

Front 20

Does this code work?

"Welcome To Java".length();

Back 20

yes. Java can treat that as a literal

Front 21

Besides using s1.concat(s2) what's another way to concatenate two strings?

Back 21

s3 = s1 + s2 + " hi!";

Front 22

When using + to concatenate, what happens if one of the values is not a string?

Back 22

It is turned into a string and treated as one

Front 23

Difference between next() and nextLine() when reading strings from console

Back 23

inputVar.next(); reads a string that ends with whitespace

inputVar.nextLine(); reads an entire line of text

Front 24

What shouldn't nextLine() be used after nextInt(), nextDouble(), etc.?

Back 24

You'll get an input error

Front 25

How do you read a character from the console?

Back 25

input.nextLine();

then use stringVar.charAt(0); to get the character

Front 26

s1.equals(s2);

s1.equalsIgnoreCase(s2);

s1.compareTo(s2);

s1.compareToIgnoreCase(s2);

startsWith(prefix);

endsWith(suffix);

contains(s1);

Back 26

equals(s1): true if s1 = s2

equalsIgnoreCase(s1): ignores case

compareTo(s1); returns int > 0, < 0, or = 0 to indicate whether >, <, =

compareToIgnoreCase(s1);

startsWith(prefix): true if starts w/ that prefix

endsWith(suffix): true if ends w/ that suffix

contains(s1): true if substring is in string

Front 27

What does this do?

string1 == string2;

Back 27

checks whether they refer to same object, not whether contents are the same

Front 28

Can you use relational operators with strings in Java?

Back 28

NO

Use .compareTo(s1)

Front 29

Methods in the String class for obtaining substrings

substring(beginIndex);

substring(beginIndex, endIndex);

Back 29

returns substring that begins w/ character at the specified starting index and extends until end of string ("hello there") starting at 2 --> ("lo there")

returns substring that begins w/ char at specific starting index and extends until ending index

Front 30

Methods in the String class for obtaining substrings

index(ch);

indexOf(ch, fromIndex);

indexOf(s);

indexOf(s, fromIndex);

Back 30

index(ch): returns indx of first occurence of char in string (-1 if not found)

indexOf(ch, fromIndex): starts at that indx

indexOf(s): returns indx of first occurence of substring

indexOf(s, fromIndex): starts at that index

Front 31

Methods in the String class for obtaining substrings

lastIndexOf(ch);

lastIndexOf(ch, fromIndex);

lastIndexOf(s);

lastIndexOf(s, fromIndex);

Back 31

lastIndexOf(ch): returns indx of last occrnce of char in string (-1 if not found)

lastIndexOf(ch, fromIndex): starts at that indx

lastIndexOf(s): returns indx of last occrnce of substring in string (-1 if not found)

lastIndexOf(s, fromIndex): starts at the indx

Front 32

How do you convert a numeric string into an int or double?

Back 32

Integer.parseInt(myIntString);

intString is something like 123 (int numeric string)

Double.parseDouble(myDoubleString);

doubleString is something like 123.45 (double numeric string)

Front 33

If you try to convert a non-numeric string into a number, what happens?

Back 33

runtime error

Front 34

printf can be used with ____ ______ to format output

Back 34

format specifiers

Front 35

What is each part of this format specifier?

System.out.printf("%4.2f" + variable);

Back 35

%: start of format specifier

4: field width

.2: precision

f: actual format specifier

Front 36

Format Specifiers

%b

%c

%d

%e

%f

%s

Back 36

%b boolean

%c char

%d decimal integer (e.g., 200)

%e scientific notation

%f floating-point number

%s string

Front 37

System.out.printf("count is %d and amount is %f", count, amount);

Back 37

count is a decimal integer

amount is a floating-point

Front 38

%5c

Back 38

field width is 5, so add 4 spaces before the 1 char

Front 39

%10.2e

Back 39

Output the floating-point item with width at least 10 including a decimal point, twodigits after the point and the exponent part. If the displayed number in scientificnotation has width less than 10, add spaces before the number.

Front 40

By default, output is right-justified. How do you make it left-justified?

Back 40

-

%-5.2f

%-10s

Front 41

True or false: items have to exactly match format specifiers

Back 41

true

Front 42

% denotes format specifier. How do you output a literal % in the format string?

Back 42

%%

Front 43

ASCII Unicode positions

blank space

Back 43

32

Front 44

ASCII Unicode positions

0-9

Back 44

48-57

Front 45

ASCII Unicode positions

A-Z

Back 45

65-90

Front 46

ASCII Unicode positions

a-z

Back 46

97-122

Front 47

ASCII Unicode positions

Difference between uppercase letter and its lowercase counterpart

Back 47

32

Front 48

How do you convert a String object to a character array?

Back 48

str.toCharArray();

Front 49

How do you convert a character array back to a String object?

Back 49

String.valueOf(charArrayName, starting position, number of letters)

can also use String object class

charArrayName = new String (charArrayName);

varName.toString();

Front 50

How do you replace one character with another in a String?

Back 50

.replace('E', 'Y')

Front 51

How do you terminate a program?

Back 51

System.exit(0);

Front 52

for-loop in Java vs. C++

Back 52

The C++ version will work, but Java prefers a test where it can use length

int [] arr = new int[];

for (int x=0; x

Front 53

Arrays must be dynamically allocated in Java because they are created in the ____, not the _____

Back 53

heap not stack

Front 54

All methods in Math return type

Back 54

double
cast to int if needed

Front 55

Strings: compareTo

What does it return if they're equal? First is superior? First is inferior?

Back 55

Equal: returns 0First is superior: returns positive numberFirst is inferior: returns negative number

Front 56

Compare:

Scanner input = new Scanner(System.in);

(char)System.in.read();

Back 56

both will read input. The 2nd expects you to enter a single character and returns an integral value, but we're casting to char