CMPS 161/280

Question 1

What is an Object?

Answer 1

a self-contained component that contains properties and methods needed to make a certain type of data useful. An object’s properties are what it know and its methods are what it can do.

Question 2

What is a Class?

Answer 2

a blueprint or template or set of instructions to build a specific type of object. Every object is built from a class.

Question 3

What is instantiation?

Give an example.

Answer 3

The process of a class being used to create an object.
SimpsonsCharacter bart = new SimpsonsCharacter();

Question 4

What does the Public access modifier mean?

Answer 4

Any class can refer to the field or call the method.

Question 5

What does the Private access modifier mean?

Answer 5

Only the current class will have access to the field or method.

Question 6

What does the Protected access modifier mean?

Answer 6

Only the current class and subclasses of this class will have access to the field or method.

Question 7

What is a Method?

What is the syntax for a Method?

Answer 7

Syntax: {access} {use} {return type} methodName({parameters})

Behavior of objects are represented as methods.
 methodName(parameters)
{
     method body;
}

Question 8

What are the return types for a method?

Answer 8

Int, String, Boolean, Object, void?

Question 9

What is a static method?

Answer 9

Static methods are meant to be relevant to all instances of a class rather than to any specific instance. They are called “static” because they are resolved at compile time based on the class they are called on. They can’t be overriden.

Question 10

Considering Arguments, what is Pass by Value?

Answer 10

Making a copy in memory of the actual parameter’s value that is passed in, a copy of the contents of the actual parameter.

Question 11

Considering arguments, what is Pass by Reference?

Answer 11

A copy of the address of the actual parameter is stored. Use pass by reference when you are changing the parameter passed in by the client program.

Question 12

What are the 8 basic data types in Java?

Answer 12

byte, short, int, long, float, double, boolean, char

Question 13

What is the Byte data type?

Answer 13

Byte data type is an 8-bit signed two’s complement integer.

Minimum value is -128 (-2^7)
Maximum value is 127 (inclusive)(2^7 -1)

Example: byte a = 100 , byte b = -50

Question 14

What is the Short data type?

Answer 14

Short data type is a 16-bit signed two’s complement integer.

Minimum value is -32,768 (-2^15)

Maximum value is 32,767 (inclusive) (2^15 -1)

Example: short s = 10000, short r = -20000

Question 15

What is the int data type?

Answer 15

Int data type is a 32-bit signed two’s complement integer.

Minimum value is - 2,147,483,648.(-2^31)
Maximum value is 2,147,483,647(inclusive).(2^31 -1)

Example: int a = 100000, int b = -200000

Question 16

What is the long data type?

Answer 16

Long data type is a 64-bit signed two’s complement integer.

Minimum value is -9,223,372,036,854,775,808.(-2^63)
Maximum value is 9,223,372,036,854,775,807 (inclusive). (2^63 -1)

Example: long a = 100000L, long b = -200000L

Question 17

What is the float data type?

Answer 17

Float data type is a single-precision 32-bit IEEE 754 floating point.

Float is mainly used to save memory in large arrays of floating point numbers.

Example: float f1 = 234.5f

Question 18

What is the double data type?

Answer 18

double data type is a double-precision 64-bit IEEE 754 floating point.

This data type is generally used as the default data type for decimal values, generally the default choice.

Example: double d1 = 123.4

Question 19

What is the boolean data type?

Answer 19

boolean data type represents one bit of information.

There are only two possible values: true and false.

This data type is used for simple flags that track true/false conditions.

Example: boolean one = true

Question 20

What is the char data type?

Answer 20

char data type is a single 16-bit Unicode character.

Minimum value is ‘\u0000’ (or 0).

Maximum value is ‘\uffff’ (or 65,535 inclusive).

Char data type is used to store any character.

Example: char letterA =’A’