Finals Notes I

Question 1

What is a compiler language? Name an example.

Answer 1

• Input is a whole program
• Code turns into several binary code steps
• C++

Question 2

What is an interpreter? Name an example.

Answer 2

• Reads program instruction by instruction
• Does not make a binary executable file
• Example: Python

Question 3

What type of language is Java?

Answer 3

• Hybrid of both compiler and interpreter.
• Compiles into byte code.
• Byte code is read by a JVM.

Question 4

What would give this error?
Main method not public.

Answer 4

Forgotten the word “public”

Question 5

Why would an error occur here?
public static main(String[] args)

Answer 5

Forgetting the word “void”

Question 6

What is a compile-time error? Name some examples.

Answer 6

• Detected by the JVM before the program runs
• Examples: Syntax errors like missing symbols or type mismatches

Question 7

What is a runtime error? Can you name some examples.

Answer 7

• Occurs after a program compiles
• Happens while a program is being executed
• Examples: dividing by zero, null references, invalid indexes

Question 8

How can you name a variable?

Answer 8

• Starting with a letter, $, or _.
• Generally in lowerCamelCase

Question 9

int a, b;
a = 1234;
b = 99;
int c = a + b;

What are the variables, literals, declaration / assignment / combined statements?

Answer 9

a and b
1234 and 99
int a, b
a = 1234 and b = 99
int c = a + b

Question 10

What does the word “final” do?

Answer 10

Prevents a variable from being altered.

Question 11

What is a trace?

Answer 11

A table of variable values after each statement in a code.

Question 12

What is the difference in declaring a char versus a String?

Answer 12

char uses ‘’ while String uses “”

Question 13

What is a primitive type? Name an example.

Answer 13

• Basic type
• Stories primitive values
• Does not have associated methods
• Example: char

Question 14

What is a reference type? Name an example.

Answer 14

• Instantiable classes that use primitive types
• Reference variables store the address
• Have associated methods
• Example: String

Question 15

How do primitive and reference types store data?

Answer 15

Primitive types store actual values while reference types store the reference or “arrow” to an address

Question 16

Can doubles be assigned integer values?

Answer 16

Yes. The integer is automatically converted to a double.

Question 17

What is the difference between 5/2.0 and 5.0/2?

Answer 17

They are treated the same. Only one of the numbers has to be a double for the answer to be a double.

Question 18

What is the difference between 5/0 and 5.0/0?

Answer 18

ArithmeticException vs. Infinity