Midterm 1

Question 1

Algorithm

Answer 1

a set of unambiguous and ordered steps to accomplish a task

Question 2

3 control structures

Answer 2

Sequence (i.e. one line after the other)
Decision making (e.g. using if/else constructs)
Looping (e.g. using while loops)

Question 3

Algorithm development should be independent of…

Answer 3

the final computer language used to implement the algorithm as an executable program

Question 4

Java

Answer 4

• an object-oriented programming language
• portable between machines
  
  • > compiled into Java bytecode. This is a machine code for a “virtual computer” called the Java Virtual Machine (JVM).
  • > JVM interpreter reads bytecode and simulates its execution.

Question 5

Object

Answer 5

The principal entities that are manipulated by a Java program

Question 6

Class

Answer 6

• A blueprint or template for the structure of an object.
• The structure around which all Java programs are based.
• combination of data units (variables) and computation units (methods)

Question 7

Method

Answer 7

• Java’s term for a procedure or subroutine. Every method belongs to some class, and a class may have any methods.
• Each method has a name, a list of arguments enclosed in parentheses, and body, enclosed in curly braces.

Question 8

Main Method

Answer 8

There must be exactly one method called main. This is where execution begins

Question 9

Statements (4 examples)

Answer 9

Individual instructions. Examples:

- Declarations -> declare (and initialize) variables
- Assignment -> compute and assign a new value to a variable    - Method invocation -> execute a method (which may return a result)    - Control flow -> alter the order in which statements are executed

Question 10

Variables

Answer 10

Data items that the methods operate on. Variables can be of various types, integers

Question 11

Expressions/ Operators

Answer 11

Java provides various operators, which allow you to manipulate the variables
x = (2 * y - z) / 32;

Question 12

Types of errors

Answer 12

Compile time and Run time

Question 13

Compile time error

Answer 13

• caught by Eclipse / Java compiler
• Syntax errors
• Disobeys the rules of the language; violates language’s grammar
• Type errors: misuse of variables

Question 14

Run time error

Answer 14

• appear during program execution
• Obeys the rules of the language but does not express them meaning you intended;
• Division by 0
• Crash or hang or wrong outputs (b/c of mistakes in programming)

Question 15

What is variable? (4)

Answer 15

• name of some location of memory used to hold a data value.
• Different types of data require different amounts of memory. Compiler’s job is to reserve sufficient memory
• Variables need to be declared once
• Variables are assigned values, and these values may be changed later
• Each variable has a type, and operations can only be performed between compatible types.

Question 16

Variable Name (rule

Answer 16

1. Starts with: a letter (a-z or A-Z), dollar sign ($), or underscore (_)
2. Followed by: zero or more letters, dollar signs, underscores, or digits (0-9)
3. Uppercase and lowercase are different (total =/= Total =/= TOTAL)
4. Cannot be any of the reserved names (class, float, int, if, then, else, do, public, private, void,…)

Question 17

Primitive Data Types

Answer 17

Integer Types: byte, short, int, long
Floating-Point Types (real numbers): float, double
Other types: boolean, char

Question 18

Escape sequences

Answer 18

Allows us to include single/double quotes and other special characters:
" double quote
' single quote
\ backslash
\n new-line character (starts a new line)
\t tab character

Question 19

String Comparison

Answer 19

Strings should not be compared using operators (==, <=, returns true if s equals t
s.length() -> returns length
s.compareTo(t) -> compares strings lexicographically
result < 0 if s is less than t
result == 0 if s is equal to t
result > 0 if s is greater than t

Question 20

Scanner Class operations

Answer 20

nextBoolean()
nextByte()
nextDouble()
nextFloat()
nextInt()
nextLong()
nextShort()
next() - returns sequence of characters up to next whitespace (space, carriage return, tab, etc.)
nextLine() - returns sequence of characters up to next carriage return

Question 21

Control flow

Answer 21

The order in which statements are executed
General rule -> top to bottom
Several control structures that change that

Question 22

Conditional statements

Answer 22

permit control flow to be dependent on (true/false) conditions

• if
• if-else