Week 3

Question 1

Objects are defined by

Answer 1

classes rather than a primitive type. (variables can be used to store primitive types).

Question 2

objects are created with the…

Answer 2

new operator and a variable that can then be assigned to reference the object.

Question 3

an object variable is a…

Answer 3

reference variable. It doesn’t hold the object but rather the memory location where the object is.

Question 4

creating an object is called

Answer 4

instantiation

Question 5

an object is a(an) _________ of a particular class

Answer 5

instance

Question 6

objects unlike primitives can have what?

Answer 6

methods.

• provide functionality – ex. The nextInt() method reads user input
• invoked using the dot operator
• a method may return a value int count = title.length()
• a method may accept parameters as input myScan.userDelimiter(“, “)
• may have both a return value and parameters

Question 7

Assignment takes a …

Answer 7

copy of a value and stores it in a variable

Question 8

two or more references are called what?

Answer 8

aliases

Question 9

What happens when when an object no longer has any references to it?

Answer 9

it can’t be accessed and is called garbage.

Question 10

immutable

Answer 10

String objects cannot be changed in memory once created.

Question 11

the replace() method

Answer 11

returns a whole new String object

String title = title.replace(“s”, “S”);

Question 12

String Indexes

Answer 12

• Characters are indexed starting at 0.
• you can get a particular character from a String using the charAt()
• Ex. String my String = “Hello”;
• Ex. Char myChar = myString.charAt(0); this would get the H

Question 13

JCL

Answer 13

Java Class Library (JCL) is a set of classes that are part of the JDK and documented in the Java API. Classes are organized into packages (java.lang, java.applet, java.util, etc.)

Question 14

the methods of the Math class are what?

Answer 14

static methods. They can be invoked using the class name rather than an object reference. (ex. Math.sqrt(delta))

Question 15

DecimalFormat class

Answer 15

class can be used to format both floating point and integer values in various ways. The constructor takes a String that represents the pattern for formatting. The format method is called on the DecimalFormat object to return a String representing the value.

Question 16

bankers rounding in java

Answer 16

rounds to the nearest even but confusing and dumb

Question 17

Wrapper class

Answer 17

is a class whose object wraps or contains primitive data types. When we create an object to a wrapper class, it contains a field and in this field, we can store primitive data types. In other words, we can wrap a primitive value into a wrapper class object.

Question 18

autoboxing

Answer 18

the automatic conversion of a primitive value to a corresponding wrapper.
    Integer obj;
    int num = 42;	
    obj = num;
-int i = Integer.partInt(“1234”);
-double x = Double.parseDouble(“12.34”);