Develop Reference

How to get a random number in one statement from a list of values;

Given the code below I have to find a way to get a random value from the values: 100, 120, 140, 160, 180, 200, 220, 240, 260, 280. The catch is that I have to write a single statement (One semi-colon) that will randomly pick one of the ints and assign it into the random_int variable. Does anyone have any idea how I could create a list or array of the numbers above and pick a random int from the numbers to assign to random_int in a single statement? Thank you for the help!
public static void main(String[] args) {
Random random = new Random();
int random_int;
// Your single statement goes here
System.out.println(“Number is: “ + random_int);
}

You can do something like:
public static void main(String[] args) {
Random random = new Random();
List<Integer> integerList = Arrays.asList(100, 120, 140, 160, 180, 200, 220, 240, 260, 280);
System.out.println(integerList.get(random.nextInt(integerList.size())));
}

You can make use of the Arrays class to create a collection from your array
System.out.println(Arrays.asList(100, 120, 140, 160, 180, 200, 220, 240, 260, 280).
get(new Random().nextInt(10)));

Push them all into an array and random the array's index. All can be done in one single statement:
public static void main(String[] args) {
Random random = new Random();
int random_int = new int[]{100, 120, 140, 160, 180, 200, 220, 240, 260, 280}[random.nextInt(10)];
System.out.println("Number is: " + random_int);
}

public class Foo {
public static void main(String[] args) {
for (int i = 0; i < NUMBERS.size(); i++)
System.out.println(getRandomNumber());
}
private static final List<Integer> NUMBERS = Arrays.asList(100, 120, 140, 160, 180, 200, 220, 240, 260, 280);
public static int getRandomNumber() {
Collections.shuffle(NUMBERS);
return NUMBERS.get(0);
}
}

int random_int = new Random().nextInt(10)*20 + 100;
int random_int = (new Random().nextInt(10) + 5)*20;
nextInt(10) will give 0..9. (9 = (280 - 100)/20).
It is a matter of seeing the regularities in the desired numbers: steps of 20, starting with 100 upto 280.
Could have been an exam question.

Given below can be the single statement to do the job:
random_int = List.of(100, 120, 140, 160, 180, 200, 220, 240, 260, 280)
.get(random.nextInt(List.of(100, 120, 140, 160, 180, 200, 220, 240, 260, 280).size()));
Explanation:
Random#nextInt(int bound) returns an int value between 0 (inclusive) and bound (exclusive).
List#get(int index) returns the element at the specified position in this list.
List#size() returns the number of elements in this list.

Huffman code tree decoding

I'm trying to decode a huffmann binary code tree with no success. Am using the following code:
public static int decodeTree(String str){
int length = str.length();
int num = 0;
int number = 0;
Node root = tree1.get(0);
String b;
// 0 left
// 1 right
for (int x = 0; x <tree1.size(); x++) {
Node curr = root;
while ((curr.isLeaf() == false) && num < length) {
if (str.charAt(num) == '0') {
curr = curr.Left();
num++;
}
else if (str.charAt(num) == '1') {
curr = curr.Right();
num++;
}
}
number = curr.getValue();
}
return number;
}
It should output:
10, 46, 200, 155, 50, 50, 23, 12, 18, 59, 40, 10, 200, 10, 40, 50, 46, 12, 18, 200, 46
It is currently outputting:
155, 46, 200, 200, 50, 91, 23, 12, 46, 200, 40, 200, 155, 50, 200, 68, 38, 50, 18, 200, 200
It is to return decimal numbers. It decodes some numbers correctly but in the wrong sequence. Do you have any idea what might be wrong?
I'm also uploading my Tree implementation:
public static String[] huffman(int[] histo){
//initial list of nodes
tree1 = new ArrayList<>();
for (int i = 0; i < histo.length; i++)
if(histo[i] != 0) {
tree1.add(new Node(histo[i], i));
}
//get weights until only root node is left out
while(tree1.size() > 1){
combine(tree1);
}
//recursively generate code for each node in the tree
//if the recursion finds a leaf node,
//it sets the correct element in the array to the code of the node
Node root = tree1.get(0);
String[] codage = new String[histo.length];
root.genCodeWord(codage);
return codage;
}
Further information:
This is how I'm trying to decode back:
String[] oneDConvertedBack1 = new String[oneD.length];
System.out.print("\n\nCONVERTED BACK:\n");
for(int i =0; i<oneD.length; i++)
Gray graycode = new Gray();
oneDConvertedBack1[i] = graycode.convertToBinaryCode(oneDGray[i]);
}
for(int i=0; i<oneD.length;i++)
System.out.print(oneDConvertedBack1[i]+ ", ");
int[] oneDConvertedBack2 = new int[oneD.length];
System.out.print("\n\nCONVERTED BACK:\n");
for(int i =0; i<oneD.length; i++) {
oneDConvertedBack2[i] = decodeTree(oneDBinary[i]);
}
The following are the constituents of the Nodes of the tree and its CodeWord method
public Node(Node left, Node right, int value){
l = left;
r = right;
v = value;
i = -1;
}
public void genCodeWord(String[] codes){
if(l != null && r != null){
l.setCodeWord("0"+getCodeWord());
l.genCodeWord(codes);
r.setCodeWord("1"+getCodeWord());
r.genCodeWord(codes);
}else{
codes[i] = getCodeWord();
}
}

NumberFormatException trying to parse " 66" to an integer

So i have this slice of code that reads text from a csv file where nums[] goes throughout the file and stores the number of a said student, and grades[][] goes through and stores each of their grades:
Scanner sc = new Scanner(new FileReader("location.csv"));
String [][] stuff = new String [10][];
for(int i = 0; i<10; i++){
String line = sc.nextLine();
stuff[i] = line.split.(",");
}
int [][] grades = new int [10][10];
int [] nums = new int [10];
for(int x = 0; x<10; x++){
nums[x] = Integer.parseInt(stuff[x][0]);
System.out.println(nums[x]);
for(int y = 0; y<11; y++){
grades[x][y] = Integer.parseInt(stuff[x][y]);
}
}
The problem is that numbs works wonderfully, but grades cant store any value that is past the first column of data. If I set grades [x][y] = stuff[any number] [0] it will run, but if I try to go past 0 in the rows, I error terminate.
Part of data file:
1, 66, 82, 85, 87, 65, 80, 97, 75, 68, 72
2, 70, 63, 75, 62, 84, 65, 67, 95, 81, 96
3, 100, 98, 73, 78, 69, 75, 97, 66, 61, 90
4, 75, 62, 79, 78, 87, 73, 74, 76, 63, 84
5, 81, 90, 80, 66, 75, 96, 73, 77, 66, 87
Stack Trace:
java.lang.NumberFormatException: For input string: " 66"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:481)
at java.lang.Integer.parseInt(Integer.java:527)
Fixed Code ( I apologize, I did not copy the code verbatim and included a few extra errors in it)
public static void main(String[] args)throws FileNotFoundException
{
Scanner sc = new Scanner(new FileReader("location.csv"));
String [][] values = new String [10][];
for(int i = 0; i<10; i++){
String line = sc.nextLine();
values[i] = line.split(",");
}
int [][] grades = new int [10][10];
int [] nums = new int [10];
for(int x = 0; x<10; x++){
nums[x] = Integer.parseInt(values[x][0]);
System.out.println(nums[x]);
for(int y = 0; y<10; y++){
grades[x][y] = Integer.parseInt(values[x][y+1].trim());
}
}

You aren't getting rid of the whitespace between tokens.
Make sure to clear it, preferably with String#trim()
Integer.parseInt(stuff[x][0].trim());
For the record, I'd also look to use better names than stuff.

Also, you're going to get an index out of bounds when you fix those other errors:
for( int y = 0; y < 11; y++ )
grades[x][y] = Integer.parseInt( stuff[x][y] );
All your array indexes go to 10, which in Java means 0 through 9. y here will go to 10, so boom out of bounds.
Considering the syntax errors pointed out in the comments, please in the future copy and paste the EXACT code you are using. It'll be no good if we are debugging different code than what you are actually using.

Hangman Graphics

I'm having trouble getting the graphics to show up with my hangman program.
This is the code for my engine class:
public static void main(String[] args)
{
//hangman viewer stuff
//////////////////////////////////////////////////////////////
JFrame frame = new JFrame();
frame.setSize(200,375); //invoked the method setSize on the implicit parameter frame
frame.setTitle("Hangman");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
HangmanComponent g = new HangmanComponent();
frame.add(g);
frame.setVisible(true);
///////////////////////////////////////////////////////////////
String wordd = JOptionPane.showInputDialog("Type in a word.");
int length = wordd.length();
String blank = "_ ";
String word2 = new String("");
int guesscount = 10;
ArrayList<String>answers=new ArrayList<String>(); //creates reference to empty structure that will contain references
char blanks[]=new char[wordd.length()]; //creates an array with the same number of terms as the length of the word
for (int i=0; i<length; i++)//fills the array with blanks corresponding to the length of the word
{
blanks[i] = '_';
}
HangmanComponent y = new HangmanComponent();
while (true)
{
String letter = JOptionPane.showInputDialog("Guess a letter! You have "+guesscount+" guesses."+"\n"+answers+"\n"+Arrays.toString(blanks).replace(",", " ").replace("[","").replace("]","")); //Prints a space
char letterchar = letter.charAt(0); //converts string letter to char letterchar
int idx = 0;
boolean found = false;
answers.add(letter); //adds the string to the arraylist answers
while (idx >= 0 && idx < length) //idx is greater than or equal to 0 but less than the length of the word
{
//System.out.println("idx = " + idx);
idx = wordd.indexOf(letter, idx); //idx is the index of "letter" in "wordd" and finds all instances of the letter
//System.out.println("idx = " + idx + ", guesscount = " + guesscount);
if (idx != -1) //if idx is not -1 (the letter exists in the word)
{
found = true;
blanks[idx] = letterchar; //sets the term in the array equal to the letter
idx += 1; //idx=idx+1
}
else
{
guesscount=guesscount-1;
y.nextStage();
y.printStage();
frame.add(y);
frame.setVisible(true);
break;
}
}
if (found)
{
JOptionPane.showMessageDialog(null, Arrays.toString(blanks).replace(",", " ").replace("[","").replace("]","")+"\n"+"You found a letter!"+"\n"+answers);
}
else
{
JOptionPane.showMessageDialog(null, Arrays.toString(blanks).replace(",", " ").replace("[","").replace("]","")+"\n"+"That letter is not in the word! Guess again!"+"\n"+answers);
if (guesscount == 0)
{
JOptionPane.showMessageDialog(null, "Sorry, you're all out of guesses. The answer was '"+wordd+".' Thanks for playing!");
break;
}
}
char [] lettersArray = wordd.toCharArray(); //converts word to array of chars
if (Arrays.equals(blanks, lettersArray))//compares array of blanks to array of letters
{
JOptionPane.showMessageDialog(null, "You guessed the word! Thanks for playing!");
break;
}
}
}
and this is the code for my HangmanComponent class (with the graphics)
int stage=0;
public void nextStage()
{
stage++;
}
public void printStage()
{
System.out.println("Your stage number is:"+stage);
}
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
g2.setStroke(new BasicStroke(5,BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL));
g2.setColor(Color.BLACK);
g.drawLine(50, 30, 50, 10);
g.drawLine(50, 10, 130, 10);
g.drawLine(130, 10, 130, 300);
g.drawLine(20, 300, 150, 300);
if (stage==1)
{
//draws the head
g2.setStroke(new BasicStroke(3,BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL));
Ellipse2D.Double head = new Ellipse2D.Double(25, 30, 50, 50);
g2.draw(head);
}
else if (stage==2)
{
//draws the body
g.drawLine(50, 80, 50, 180);
}
else if (stage==3)
{
//draws the left arm
g.drawLine(10, 150, 50, 100);
}
else if (stage==4)
{
//draws the right arm
g.drawLine(50, 100, 90, 150);
}
else if (stage==5)
{
//draws the left leg
g.drawLine(30, 250, 50, 180);
}
else if (stage==6)
{
//draws the right leg
g.drawLine(50, 180, 70, 250);
}
else if (stage==7)
{
//draws the left eye
Ellipse2D.Double lefteye = new Ellipse2D.Double(40, 50, 1, 1);
g2.draw(lefteye);
g2.fill(lefteye);
}
else if (stage==8)
{
//draws the right eye
Ellipse2D.Double righteye = new Ellipse2D.Double(58, 50, 1, 1);
g2.draw(righteye);
g2.fill(righteye);
}
else if (stage==9)
{
//draws the mouth
Arc2D.Double mouth = new Arc2D.Double(40.00, 50.00, 20.00, 20.00, 180.00, 190.00, Arc2D.OPEN);
g2.draw(mouth);
}
}
Right now, the hangman program runs perfectly fine, but the graphic is only added the first time the user inputs a wrong letter. How do I get the graphics to be inputted for every time a wrong letter is inputted?

Passing parameters from method to main

I can't seem to figure out what my parameters should be for my method "public static int[][] sellSeatByPrice". I need to prompt the user for a price (of a seat), then figure out if that price is taken (if it = 0) and if not, assign it the value 0.
Below is my code, help please!
import java.util.Scanner;
/**
* Write a description of class A10_TheaterSeating here.
*
* #author (your name)
* #version (a version number or a date)
*/
public class A10_TheaterSeating
{
public static void main(String args[])
{
System.out.println("***Welcome to the Ticket Choice App!***");
System.out.println();
int[][] theaterSeats = //set values in seating chart array
{
{10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
{10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
{10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
{10, 10, 20, 20, 20, 20, 20, 20, 10, 10},
{10, 10, 20, 20, 20, 20, 20, 20, 10, 10},
{10, 10, 20, 20, 20, 20, 20, 20, 10, 10},
{20, 20, 30, 30, 40, 40, 30, 30, 20, 20},
{20, 30, 30, 40, 50, 50, 40, 30, 30, 20},
{30, 40, 50, 50, 50, 50, 50, 50, 40, 30}
};
int[][] seats = theaterSeats;
printArray(seats); //print the seating chart
System.out.println();
//Defining variables
String str = "";
String input = "";
while (!input.equalsIgnoreCase("Q"))
{
System.out.print("Select 'S' to pick a seat, 'P' choose a price or 'Q' to quit: ");
Scanner in = new Scanner(System.in);
input = in.next();
if (input.equalsIgnoreCase("S"))
{
System.out.print("Enter row and seat number desired: ");
int row = in.nextInt();
int seat = in.nextInt();
System.out.println();
sellSeatByNumber(seats, row, seat);
printArray(seats);
System.out.println();
}
else if (input.equalsIgnoreCase("P"))
{
System.out.print("Enter price of seat desired: ");
int price = in.nextInt();
System.out.println();
sellSeatByPrice(seats, row, seat, price);
printArray(seats);
System.out.println();
}
}
System.out.println();
System.out.println("Thank you for choosing the ticket choice app.");
System.out.println();
}
public static void printArray(int[][] currSeat)
{
final int ROWS = 9;
final int COLUMNS = 10;
for(int i = 0; i < ROWS; i++)
{
for (int j = 0; j < COLUMNS; j++)
{
System.out.print(currSeat[i][j] + "\t");
}
System.out.println();
}
}
public static int[][] sellSeatByNumber(int[][] seats, int row, int seat)
{
if (row <= 0 || row > 9)
{
if (seat <= 0 || seat > 10)
{
System.out.print("Please enter a valid row and seat: ");
}
}
if (seats[row][seat] == 0)
{
System.out.print("That seat is taken. Please select another seat: ");
}
else
{
seats[seats.length - row][seat - 1] = 0;
}
return seats;
}
public static int[][] sellSeatByPrice(int[][] seats, int row, int seat, int price)
{
if (seats[row][seat] = price)
{
seats[seats.length - row][seat - 1] = 0;
}
return seats;
}
}

Your parameters seem fine - the internal logic and syntax is incorrect.
Since you're using static methods, and passing along the seat matrix, that is okay - but you have to check that the values being passed in are inside the bounds of your matrix - or you will get exceptions on them.
For instance, you don't check the bounds in sellSeatByPrice(). You really should do that, or a bogus row/seat combination could blow your program up.
It's also the case that the comparison given is incorrect:
if (seats[row][seat] = price)
should really be
if (seats[row][seat] == price)
as = is assignment, and == is primitive comparison.
Furthermore, in sellSeatByNumber(), you can still run into issues since an out of bounds row/seat combo will still blow up. You do check the bounds - kudos - but you don't return anything if they're outside of those bounds. In all reality, an IllegalArgumentException should be raised if they're stepping out of bounds, or you can return the matrix unmodified (which may be more straightforward).