- Writing Classes
- Constructors
- Public, Private, Protected; Access Modifiers
- this Keyword
- Inheritance, extends
- Big O notation for Hash map, Binary Search, Single loop, Nested Loop
- Implementation
class Food {
//attributes
private String cuisine;
private String name;
private int mealsConsumed;
//instance variables
//constructor
Food(String cuisine, String name, int mealsConsumed)
{
this.cuisine = cuisine;
this.name = name;
this.mealsConsumed = mealsConsumed;
}
public String getName(){
return name;
}
}
public class Foodmain {
public static void main(String[] args) {
Food newFood = new Food("Indian", "Dal", 20);
System.out.println(newFood.getName());
}
}
Foodmain.main(null)
import java.util.Scanner; //allows scanners to be in program
public class averages {
public static void main(String[] args) {
}}
Scanner in = new Scanner(System.in); //creates a scanner
System.out.print("Input 1st number: "); //asks user for input
int num1 = in.nextInt(); //saves number and goes to next int
System.out.println(num1);
System.out.print("Input 2nd number: "); //same as above
int num2 = in.nextInt();
System.out.println(num2);
System.out.println("The average of those numbers are " + (num1 + num2)/(2));
//prints out
//num you want to divide is however many numbers you want to average out
averages.main(null)
public class Main {//main class
int modelYear;
String modelName;//attributes
public Main(int year, String name) {//constructor
modelYear = year;
modelName = name;
}
public static void main(String[] args) {
Main myCar = new Main(1969, "Mustang");//objects
System.out.println(myCar.modelYear + " " + myCar.modelName);
}
}
// Outputs 1969 Mustang
Main.main(null);
//public
//Exercise 1:
//Write a program to reverse the words in a sentence
//example: the strawberry cake
//becomes: cake strawberry the
//hints: use scanner to take in words
//use split to break apart words to reverse them
import java.util.*; //import scanner
public class Main {
public static String reverse_str_order(String input_sentence) { //
if (input_sentence == null) {
throw new IllegalArgumentException("Null"); //no empty strings
}
StringBuilder stringBuilder = new StringBuilder();
String[] words = input_sentence.split(" ");
for (int i = words.length - 1; i >= 0; i--) {
stringBuilder.append(words[i]); //place words in order
if (i != 0) { //keep going until no more words are left
stringBuilder.append(" ");
}
}
return stringBuilder.toString();
}
}
public static void main(String[] args) { //prepares for scanning
Scanner scanner = new Scanner(System.in);
System.out.print("Input string: "); //asks for user input
String input = scanner.nextLine(); //takes in next line
System.out.println("\nResult: " + reverse_str_word(input));
}
//private
//Exercise 1:
//Write a program to reverse the words in a sentence
//example: the strawberry cake
//becomes: cake strawberry the
//hints: use scanner to take in words
//use split to break apart words to reverse them
import java.util.*; //import scanner
public class Main {
private static String reverse_str_order(String input_sentence) { //
if (input_sentence == null) {
throw new IllegalArgumentException("Null"); //no empty strings
}
StringBuilder stringBuilder = new StringBuilder();
String[] words = input_sentence.split(" ");
for (int i = words.length - 1; i >= 0; i--) {
stringBuilder.append(words[i]); //place words in order
if (i != 0) { //keep going until no more words are left
stringBuilder.append(" ");
}
}
return stringBuilder.toString();
}
}
public static void main(String[] args) { //prepares for scanning
Scanner scanner = new Scanner(System.in);
System.out.print("Input string: "); //asks for user input
String input = scanner.nextLine(); //takes in next line
System.out.println("\nResult: " + reverse_str_word(input));
}
//protected
//Exercise 1:
//Write a program to reverse the words in a sentence
//example: the strawberry cake
//becomes: cake strawberry the
//hints: use scanner to take in words
//use split to break apart words to reverse them
import java.util.*; //import scanner
public class Main {
protected static String reverse_str_order(String input_sentence) { //
if (input_sentence == null) {
throw new IllegalArgumentException("Null"); //no empty strings
}
StringBuilder stringBuilder = new StringBuilder();
String[] words = input_sentence.split(" ");
for (int i = words.length - 1; i >= 0; i--) {
stringBuilder.append(words[i]); //place words in order
if (i != 0) { //keep going until no more words are left
stringBuilder.append(" ");
}
}
return stringBuilder.toString();
}
}
public static void main(String[] args) { //prepares for scanning
Scanner scanner = new Scanner(System.in);
System.out.print("Input string: "); //asks for user input
String input = scanner.nextLine(); //takes in next line
System.out.println("\nResult: " + reverse_str_word(input));
}
//ex
public class Main {
int x;
// Constructor with a parameter
public Main(int x) {
this.x = x;
}
//this used to
// Call the constructor
public static void main(String[] args) {
Main myObj = new Main(5);
System.out.println("Value of x = " + myObj.x);
}
}
Big O notation for Hash map, Binary Search, Single loop, Nested Loop
- language for runtime length
-
related to efficiency
-
hashmap: single operation to obtain position of a searched element
-
- O(1)
-
binary search
-
- O(1)
-
- eliminates half the elements each time
-
single loop
-
- O(n)
-
- The next loop executes N times, if we assume the statement inside the loop is O(1), then the total time for the loop is N*O(1), which equals O(N) also known as linear time
-
nested loop
-
- O(N*N)
-
- the first loop may execute N times, but for how many first loop executes, the inner loop executes N times
//2021 FRQ 1A 3A
//unit 5
//1a
public int scoreGuess( String guess ) {
int val = 0;
int len = guess.length();
for( int i = 0; i <= secret.length()-len; i+=1){
String ck = secret.substring( i, i+len );
if( ck.equals(guess) ){
val++;
}
}
return val*len*len;
}
//3a
public void addMembers(
String[] names, int gradYear ){
for( String n : names ){
memberList.add(new MemberInfo( n, gradYear, true) );
}
}