Chapter 1 & 2

Question 0

Define Methods?

Answer 0

Groups of related statements in a class that perform a specific task. They are used to do specific tasks on their own objects and other objects. They are comparable to functions and subroutines in other languages. A well-designed method performs only 1 task.

Question 1

How are attributes in a class defined? Discuss.

Answer 1

They are defined by variables. Each object in a class has instance variables (aka object variables) that differ between objects.

Each class attribute has a single corresponding variable.

Class variables are the variables that have the same value for every object in the class.

Question 2

How do objects communicate with each other?

Answer 2

Methods. A class or object can call methods in another class or object for many reasons, including to report changes to other objects, to change something about the other object, or to ask the other object to do something.

Question 3

Define expression.

Answer 3

A statement that returns a value.

Question 4

Return value?

Answer 4

The value produced by a statement

Question 5

What punctuation groups statements in Java? What is a group of statements grouped by this punctuation called?

Answer 5

Braces, {}. A block, or “block statement”.

Question 6

Name and define the 3 types of variables in Java.

Answer 6

Instance, class, and local. Local variables are used inside method definitions or even smaller blocks of statements within a method. They cease to exist after the method or block is done being executed.

Question 7

Variable names in Java must start with ________.

Answer 7

a letter, an underscore _, or a dollar sign $

Question 8

What are the types of data that can be used for variables?

Answer 8

Primitive types (like Int, Boolean, floats, and characters), the name of a class or interface, or an array

Question 9

Types, ranges, and defs of integers, NOT ints

Answer 9

Byte–8 bits, -128 to 127 (halves of 2^8)
Short–16 bits, -32, 768 to 32,767 (halves of 2^16)
Int–32 bits, (halves of 2^32)
Long–64 bits, halves of 2^64

Question 10

What is a double re:floats?

Answer 10

A float with more decimal places

Question 11

Difference between Boolean and boolean?

Answer 11

Class versus a variable type

Question 12

Can a variable have a class as its type? How is that denoted?

Answer 12

Yes, for instance

Color hair;
String lastName= “Hopper”;

Notice the caps in the variable type

Question 13

What is a constant? What are they useful for?

Answer 13

A variable whose value never changes. Useful for defining shared values for the use of all methods of an object.

Question 14

What’s the diff between instance variables and methods versus class variables and methods?

Answer 14

Class variables occupy memory until a Java program is finished running; if a class variable references am object, that object will ALSO remain in memory. This often causes programs to run too slowly.

Question 15

Packages?

Answer 15

A way to group related classes and interfaces. They allow groups of classes to be easily referenced in other classes, as well as eliminating potential naming conflicts among classes.

By default, Java classes can refer to the ones in the java.lang package using only short names. To use classes from another package, you must use the full package name, or use the “import” command to import the package in your source code file.

Because the Color class is contained in the java.awt package, you would call this java.awt.Color.

If the entire package has been imported, you can refer to the class simply as Color.

Question 16

Interface?

Answer 16

Helps avoid problems with single inheritance. Allows a class to have behaviors that its superclass doesn’t.

Question 17

Do the methods included in am interface define the additional behavior that it allows a subclass to have?

Answer 17

No

Question 18

How do you assign values to variables?

Answer 18

=

Question 19

How do you declare a constant?

Answer 19

Use the “final” keyword before the variable declaration, and include an initial value, like

final int YAR = 15

Yar is all caps as a naming convention

Question 20

How do you present more than 1 variable or literal as the argument to println()?

Answer 20

The + combines them into one string

Question 21

3 types of comments–describe

Answer 21

Single-line–preceded by two slash characters. //. Everything after to slashes to the end of the line is considered a comment.

Multi-line–/* text. */

Javadoc–/** text. **/. Certain utilities like javadoc create a set of web page records that document the functionality of a Java class.

Question 22

How do you indicate that a literal should be a “long” integer?

Answer 22

Adding the letter L to the number, e.g.,

yarTotal=yarTotal + 4L

Adds the number 4 in the long format to the current yarTotal format.

Question 23

How do you denote binary, octal, and hex as literals?

Answer 23

Octal–add a zero to the beginning of the number

Hex–add a zero and an x to the beginning (0x)

Binary–add 0b to the beginning

Question 24

How do you notate a literal as a negative number?

Answer 24

Put the minus sign in front of the number

Question 25

All float literals are _____

Answer 25

Considered to be double type floats, unless you add an f to the end of the number, e.g., float piValue=3.14f

Question 26

How do you use exponents in floats as literals?

Answer 26

Put the letter e followed by the exponent (which can be a negative exponent) at the end of the number

Question 27

How are underscores used in large integers?

Answer 27

In place of commas

Question 28

How are character literals represented?

Answer 28

A single character surrounded by single quote marks

Question 29

A string in Java is a ______ instead of a primitive data type.

Answer 29

Object

Question 30

Give character escape codes for new line, tab, return, single/ double quotes,

Answer 30

\n, \t, \r, \', \"

Question 31

Do you have to explicitly create a new object when working with a string?

Answer 31

No.

Question 32

Expressions can be method calls? T/f

Answer 32

True

Question 33

Define modulus in Java and give its notation

Answer 33

The remainder of two numbers, uses percent sign. 20%7=6

Question 34

What is it important to be aware of when performing division?

Answer 34

Storing a division operator in an integer removed everything after the decimal. Many arithmetic operations involving integers produce an int regardless of the original operand type. Make sure your operands have the same type that you are trying to end up with

Question 35

Which side of an assignment expression is calculated before the assignment takes place?

Answer 35

The left. E.g., int x=5; x=x+2; X is now 7

Question 36

List the assignment operators

Answer 36

X+=y means x=x+y X-=y means x=x-y X*=y means x=x*y x/=y means x=x/y

Question 37

When do assignment operators not work?

Answer 37

When either side of your statement is part of a complex expression

Question 38

Give increment/decrement expressions. What do they do?

Answer 38

X=x++; x=x--; Add or subtract 1 from the variable

Question 39

What's the difference between these two expressions and why? y=++x; y=x++;

Answer 39

In the first, y is equal to the original value of x plus 1. In the second, y is simply equal to the original value of x. X is also incremented by 1 in the second expression, while y is not.

Question 40

When do the position of increment/decrement operators matter?

Answer 40

When part of a larger expression

Question 41

Why is "assigning x to y before x is incremented" not totally correct for this expression? y=x++

Answer 41

Because Java evaluates everything on the right side of the expression before assigning a value to the left.

Question 42

Give Boolean comparison operators

Answer 42

``` == equals != does not equal < less than > greater than = greater than or equal to ```

Question 43

Give Boolean operators for each of the logical combinations.

Answer 43

AND is && or &. && involves no work on the expression on the right side of the && if the left side is false. OR is | or ||. || involves no work on the right side of the || if the left is true XOR is ^ NOT is !. It simply reverses, e.g., If yar>30 is true, then !(yar>30) returns false.

Question 44

What is a shorthand way to append something to the end of a string?

Answer 44

+= e.g. yar=yar+"Vern"; Would be equivalent to yar+="Vern";

Question 45

What are character escape codes?

Answer 45

Used for character string literals for characters that don't easily map to a specific character (like return, tab, new line, etc.)

Question 46

Can string literals include character escape codes?

Answer 46

Yes, e.g., string mike="I said, \"io soy tu padre!\"";

Question 47

Are strings stored as objects when used?

Answer 47

Not the basic types

Question 48

Increments and decrements are called _____ if listed before a variable name, and ______ if listed after.

Answer 48

Prefix, postfix

Question 49

Parentheses are used for___, periods are used for______, and square brackets are used for ______.

Answer 49

Grouping expressions Access to methods and variables within objects and classes Arrays

Question 50

Instanceof operator?

Answer 50

Returns true or false depending on if the object is an instance of the named class or any of its subclasses

Question 51

The new operator?

Answer 51

Used to create new instances of a class

Question 52

<< >> >>>

Answer 52

Bitwise left and right shift?

Question 53

?;

Answer 53

Ternary operator

Question 54

Define "statement"

Answer 54

A simple command that causes something to happen

Question 55

Define variable

Answer 55

A place where information can be stored while a program is running

Question 56

How do you declare several variables of the same type in the same statement?

Answer 56

Separate by commas, like this Int age, weight, height; Or even assign values, like so int age=35, weight=150, height=57;

Question 57

The concatenation operator can_____

Answer 57

Handle any variable or object value as if it were a string. If any part of a concatenation operation is a String or string literal, all elements of the operation are treated like strings

Question 58

Operator precedence, give full list

Answer 58

. [ ] ( ) ++ -- ! ~ instanceof. new (type)expression. The new oper. */% + - << >> >>> Bitwise < > = Relational comparison == != Equality &. AND ^ XOR | OR && Logical AND || Logical OR ? : Ternary operator = += -= *= /= %= ^= Various assignments &= |= <>= >>>= More assignments