Unit 2: Using Objects Flashcards
A _____ is an instance of a class with defined ______
object, attributes
A _____ is the formal implementation, or blueprint, of the attributes and behaviors of an object
class
Used to initialize the attributes of an object
constructor
information passed/declared for a constructor within its parentheses
ex. public Person (int height, String name, boolean home)
formal parameters
keyword used to make a new object
new
A ____ has no parameters and sets the instance variables for the object to default values
no-argument constructor
ex. Dog ted = new Dog();
The value an initialized variable has, or can be as a placeholder
null
Define the behaviors for all objects of a class and consist of a set of instructions for executing the behavior
methods
Methods that don’t have return values, so they just perform a action
void methods
constructors with the same name, but different parameters
overloading constructors
(CANNOT have two with the exact same parameters and name)
Methods that return a value that is the same type as the value given to manipulate (saved as variable, DOES NOT print calculation)
non-void methods
ex. average = calculation for average;
return average;
String objects are _____.
immutable (no method can change the value of that particular String object)
command to print a new line in java in a string
\n
value returned by indexOf() method if string doesn’t contain letter/phrase
-1
String method that returns a substring from the first index value to the last index value minus 1
String substring(int from, int to)
String method that returns a substring from the index value to the end of the string
String substring(int from)
( returns substring(from, length) )
method that tests if strings are the exact same letters in the exact same order
word1.equals(word2);
(note: put boolean in front to return true or false if they equal/don’t equal)
String .compareTo Values (tests which strings come before another by length)
> 0 :
= 0 :
< 0 :
> 0 : longer than other string
= 0 : equal to other string
< 0 : shorter than other string
(note: all in reference to 1st string)
methods that belong to a class instead of objects of a class
static methods
Math.random() returns ____.
A double that is between 0.0 inclusive and less than 1.0
Basic format for making a new object:
className objectName = new className(parameters);
The first index of a string is ___.
0
line of code used to make a substring:
What index values does the substring take?
str.substring(x, y);
from x to the index value before y
line of code to tell you length of substring:
str.length();
function to get a random number:
what values does it make?
what do you have to do to make them whole values?
- Math.random();
- random number including 0 but less than 1.0
- usually gets cast to (int)
function to take absolute value:
function to take square root:
function to use exponent:
- Math.abs(num);
- Math.sqrt(num);
- Math.pow(num, exponent);
formula to know range of numbers for Math.random()
(max number - min number + 1)
add the first number in range, multiply math by the parentheses
