Java Programming

Question 1

What does IDE stand for?

Answer 1

Integrated Development Environment

Question 2

What file type is java source code stored in?

Answer 2

.java files

Question 3

What happens during compiling?

Answer 3

.java file is compiled to produce a .class file. The .class file is then interpreted by the Java Virtual Machine

Question 4

What is in a .class file?

Answer 4

a sort of generic machine language called Java Byte Code

Question 5

What are the benefits of .class files?

Answer 5

very portable: anyone with a JVM can run it on any platform
secure: .class file is unreadable to humans

Question 6

How do you run a java program you write on the command prompt?

Answer 6

javac <programName>.java -> compiles the code (to get the .class file)</programName>

java <programName> -> interprets the compiled code and runs your program</programName>

Question 7

How do you write a string that must be broken up over multiple lines.

Answer 7

You cannot break a String literal over two or more lines. You must use the + operator

Question 8

What are the primitive types?

Answer 8

integer types: int, long, short, byte
floating point types: double, float
others: char, boolean

Question 9

When should you use and integer type other than int?

Answer 9

long should be used when you require numbers above 2 billion or below -2 billion. You must put an L at the end of a literal bigger than 2 billion

Question 10

What type does 1.0 default to?

Answer 10

Double. To get a float, you must put an f at the end

Question 11

What do you get from
‘a’ + true
‘a’ + 1

Answer 11

error
‘b’

Question 12

how do you store a number as a string?

Answer 12

you must put it in quotes for literals or cast it with Integer.toString(variableName) or ““+variableName

Question 13

What does the static keyword do?

Answer 13

Makes it into a global variable that is accessible anywhere in the class

Question 14

What are the formatting codes?

Answer 14

%d - print a decimal integer here
%6d - use at least 6 characters to do that
%f - print a floating point value here
%6f - use at least 6 characters to do that
%6.2 - with exactly 2 of them after the decimal point
%s - print a String here
%n - print a newline character

Question 15

How do you get a string input from the console?
What about an int?

Answer 15

Scanner in = new Scanner(System.in);
in.nextLine();
in.nextInt();

Question 16

What are some escape characters?

Answer 16

\ - gives a backslash character
\n - gives a newline character
\t - gives a tab character

Question 17

What are some String methods?

Answer 17

s.equals(“string”);
s.equalsIgnoreCase(“string”);
s.length();
s.charAt(1);