Building Blocks

Question 1

Java compile command?

Answer 1

javac

Question 2

What is compiler command for setting the compile output directory?

Answer 2

-d

Question 3

How does typical compile command look like? What are its parts?

Answer 3

1. -d for output directory
2. name of class we compile or package path to class or package path with * for all classes in that package
3. -cp or -classpath or –class-path for dependency folder or folder where is application built

Question 4

How to set classpath location while using compiler command and all its variants?

Answer 4

-cp
-classpath
–class-path

Question 5

How to run Java application using CLI?

Answer 5

java

Question 6

What do you need to provide “java” command to run Java application?

Answer 6

Package path to class that has main method we want to run, and complete classpath

Question 7

How do text block look like?

Answer 7

”””
text block”””

Note: it needs to have first line below opening quotes!

Question 8

In text blocks, how do we request a new line in output?

Answer 8

\n

Question 9

In text blocks, how do we request not to add a new line?

Answer 9

\

Question 10

In text blocks, how do we escape characters?

Answer 10

\ and some character
eg. "

Question 11

In text blocks, how do we request two spaces in output?

Answer 11

\s

Question 12

What is command to JAR a Java application?

Answer 12

jar

Question 13

How do we choose dependency folder while using “jar” command?

Answer 13

-c

Question 14

How do we JAR a Java application?

Answer 14

jar -cvf JarName.jar -c dependency/folder .

Question 15

What is alternative to “-cvf”

Answer 15

–create –verbose –file

Question 16

What do we need to watch out when using imports?

Answer 16

We need to look for imports with the same name

Question 17

What are rules when using wildcard * in imports?

Answer 17

• can only import classes, not subpackages.
  When specific import is defined, it trumps wildcard.

Question 18

What are rules when naming identifiers?

Answer 18

• Name cannot start with numbers
• Symbols at start can only be $ or _
• _ cannot be used as name
• Reserved keyword cannot be used as name

Question 19

What are rules for local variables?

Answer 19

They must be initiated before use

Question 20

Where can “var” be used?

Answer 20

Only with local variables

Question 21

What is rule when using “var”?

Answer 21

Its value must be set in the same line as var, not later

Question 22

Is “var” reserved keyword?

Answer 22

No, it can be used as identifier - var var = new Var();

Question 23

public int addition(var a, var b)?

Answer 23

var cannot be used as parameter as parameters are not local variables

Question 24

What is rule for initialization of variables in same line?

Answer 24

Only one variable type can be defined per line - int a, b, c = 5

Question 25

What is the order of instance initialization?

Answer 25

• Fields and instance initializers ({}) are initialed in order they appear in class
• Constructor is initialized after them

Question 26

When are static initializers being run?

Answer 26

When class is first loaded

Question 27

When are instance initializers being run?

Answer 27

When new class instance is being defined

Question 28

What are Java primitives?

Answer 28

boolean
byte
short
char
int
long
float
double

Question 29

What two primitives are similar?

Answer 29

char and short, both 16 bit

Question 30

How do we call numbers in Java?

Answer 30

Literals

Question 31

What are signed and unsigned primitives?

Answer 31

Those primitives that go from negative number to positive number (as range)

Question 32

How do we parse a primitive?

Answer 32

eg. parseInt() etc.

Question 33

How do we return wrapping class from primitive?

Answer 33

with “valueOf()” method

Question 34

How can primitives also be written?

Answer 34

• hexadecimal
• octal
• binary

Question 35

How do we write binary literals?

Answer 35

0b0101
0B1010

Question 36

How do we write hexadecimal literals?

Answer 36

0xF23

Question 37

How do we write octal literals?

Answer 37

012
053
032

Question 38

java.lang package

Answer 38

Doesnt need import, it is auto. imported