Section 1
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Escape Sequences: \'
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Date created
Mar 1, 2020
Cards (60)
Section 1
(50 cards)
Escape Sequences: \'
outputs: '
Escape Sequences: \"
outputs: "
Escape Sequences: \b
deletes previous character (backspace)
Math return methods:
floor(x) rounds x down ceil(x) rounds x up pow(x,y) returns x to the power of y abs(x) returns the absolute value of x sqrt(x) returns the square root of x round(x) rounds x to the nearest whole number min(x,y) returns smallest of x and y max(x,y) returns biggest of x and y random() returns a double >=0.0 and < 1.0 (random will give you a number from 0.0 to 0.99, not 1.0) (everything needs to start with Math.)
Boolean conditions used:
== equal != not equal <= less than or equal to >= greater than or equal to || or && and (if you are comparing strings use .equals)
How do you write a If Else statement?
if( boolean condition placed here ) { do something 1; } else { do something 2; }
Formatting Output out.printf( " %9.2f " , 8.25612 );
out.printf( " %9.2f " , 8.25612 ); 9 = column size .2 = # of decimals f = data type output == 8.26
Constructors/Zero arg constructor
Constructors set the properties of an object to an initial state. (often have parameters) public Triangle() { sideA=0; sideB=0; sideC=0; }
what will this command do?: abdi++;
it will increase abdi's value by one.
More String methods
indexOf( str ) returns the loc of String str in the string, searching from spot 0 to spot length-1 indexOf( ch ) returns the loc of char ch in the string, searching from spot 0 to spot length-1 lastIndexOf( str ) returns the loc of String str in the string, searching from spot length-1 to spot 0 lastIndexOf( ch ) returns the loc of char ch in the string, searching from spot length-1 to spot 0
How do you compare two strings?
you would use .equals() EX: String stringOne = "big"; if( stringOne.equals("it") ) { System.out.println("== it"); } if( stringOne.equals("big") ) { System.out.println("== big"); }
length()
returns the # of chars
Given the following statement, var must be defined as which of the following types? var=keyboard.nextInt();
int (Also, in the code "nextInt", "Int" has to be capitalized.
long
64 bits, big to big
What is the output by the code below? String s = "Hello"; System.out.println("\String s");
There is no output due to a syntax error. ( can't have those backslashes in the middle of code)
substring(x,y)
returns a section of the string from x to y not including y
Given the following statement, var must be defined as which of the following types? var = keyboard.nextLine();
String (for both nextLine & next you get a string)
What is casting and what is an example of casting?
Casting is often used to create compatibility among data types. EX: int one =0; double = 7.756; one=(int)dec;
char
16 bits, 0 - 65535
Byte
8 bits, -128 to 127
logical operators: !x
True if x is false
How would you create a FOR LOOP?
for(init value; boolean condition; increment) { doSomething(); } -the (init value) would be the starting number of times it will run -(boolean condition) decides when the loop stops running. the (increment) is the amount a value increases to end make the boolean condition true.
substring(x)
returns a section of the string from x to length-1
Short
16 bits, -327 to 327
Int
32 bits, -2 billion to 2 billion
How many methods does class CS contain? public class CS { public void one() { System.out.print("one"); } }
1
what are instantiation?
When you create a way to reference a method and/or code. EX: AplusBug dude = new AplusBug();
How do you assign a variable without using a data type?
abdi = 19;
charAt(x)
returns the char at spot x
What of the following is not a legal reserved word for a java data type?
integer (cause it it's "int" not integer)
What is output by the following code given the input 11 15 25 30 Scanner kb = new Scanner( System.in ); kb.nextInt(); System.out.println( kb.nextInt() );
15 (cause another command is inside the System.out.println, duuuuuhhh)
Which of the following lines correctly defines an integer variable?
int abdi = 16;
Which of the following lines correctly defines a String variable?
String s = "aplus";
Operators used in math and examples:
+ addition - subtraction * multiplication / division % modulus num = 45; out.println(num%10); 5 out.println(num/10); 4
reference
32 bitsl N/A
In Java, every program statement ends with a what ?
;
What is encapsulation?
All data members should have private access. A set of public methods should be provided to manipulate the private data.
Methods frequently used for strings:
equals(s) checks if this string has same chars as s compareTo(s) compares this string and s for >,<, and == trim() removes leading and trailing whitespace replaceAll(x,y) returns a new String with all x changed to y toUpperCase() returns a new String with uppercase chars toLowerCase() returns a new String with lowercase chars
double
64 bits, big to big
Escape Sequences: \r
moves in front of current line
logical operators: x&&y
both x and y must be true
Example of lowercase method:
char c = 'e'; out.println(c); c = Character.toUpperCase(c); Output: e
Arrays in Strings
A string is a group of characters. The first character in the group is at spot 0 and the last character is -1.
How do you create a IF switch statement? and how does it work?
int num = 30; switch(num) { case 11: System.out.println("num == 11"); break; case 30: System.out.println("num == 30"); break; } (This switch statement will check if num is equal to 11 and 30(case 11 & 30) if it is, it will print out the corresponding text, AND if it does not have a break; all conditons after the true statement will be executed untill the end or break; )
float
32 bits, big to big
Escape Sequences: \\
outputs: \
Does PEMDAS affect the math equations?
Yes, you need to follow the rules of PEMDAS
String instantiation
String s = "apluscompsci"; or String champ = new String("aplus"); s or champ is the reference variable. EX: String s = "apluscs"; int len = s.length(); System.out.println( len );
Which of the following is the newline character?
(remember, it is a backslash)
logical operators: x||y
either x or y must be true
Section 2
(10 cards)