Develop Reference

How to Delete a Record from a csv file with arrays in java

I just want to know when you overwrite the elements for deleting a certain element , you change the position of all the elements after it.The thing is when you change the position the last element in the last element will be same as the second last. here in this code i am changing the last element to be empty which i don't want . I just want to remove it so i can save it in csv. If i write null then it saves 'null' in csv as a record which i dont want! Please help!
public static void deleteEntry() {
int flag = -1;
Boolean found = false;
System.out.println("Please provide the name of the contact to delete its entry: ");
String searchName2 = sc.next().toUpperCase();
System.out.println(counter);
try {
for (int i = 0; i < counter; i++) {
if (names[i].compareTo(searchName2) == 0) {
flag = i;
found = true;
}
}
} catch (Exception e) {
}
if (flag == -1) {
System.out.println("Contact Name NOT Found");
} else { //record was found, flag is a positive index position
//if the record is the last record, simply remove it and decrement the counter
if (flag == counter - 1) {
System.out.println("Contact Deleted!");
names[flag] = null;
numbers[flag] = null;
counter--;
}else {
//record is not the last record, shift all later records down
for (int i = flag; i < counter-1; i++){
names[i] = names[i + 1];
numbers[i] = numbers[i + 1];
}
System.out.println(counter);
System.out.println("Contact Deleted!");
if (names[counter-1].equals(names[counter-2])) {
names[counter-1] = "";
numbers[counter-1] = "";
}
}
}

Head First Java book battleship game

I am reading "Head First Java" book and I came across the problem in chapter 5 with the battleship game (with simple version). I knew that the book's code doesn't work and I tried my self fixing it, but it still didn't work.
So tried to google it and I found some post on this website but I still have a problem. The game isn't working properly as it should.
If a player enters any random number, the output is always "hit"...
This is the last version of the code:
DotCom class:
public class DotCom {
private ArrayList<String> locationCells = new ArrayList<>();
public void setlocationCells(int[] loc) {
if (loc != null)
for (int val : loc)
locationCells.add(String.valueOf(val));
}
public String checkYourself(String userInput) {
String result = "miss";
int index = locationCells.indexOf(userInput);
if (index >= 0) {
locationCells.remove(index);
}
if (locationCells.isEmpty()) {
result = "kill";
} else {
result = "hit";
}
System.out.println(result);
return result;
}
}
DotComGame class:
public class DotComGame {
public static void main(String[] args) {
int guessingTimes = 0;
DotCom dot = new DotCom();
GameHelperrr helper = new GameHelperrr();
int randomNum = (int) (Math.random() * 5);
int[] locations = { randomNum, randomNum + 1, randomNum + 2 };
dot.setlocationCells(locations);
boolean isAlive = true;
while (isAlive == true) {
String guess = helper.getUserInput("Enter a number");
String result = dot.checkYourself(guess);
guessingTimes++;
if (result.equals("kill")) {
isAlive = false;
System.out.println("You took " + guessingTimes + " guesses");
}
}
}
}
I would really appreciate to get a detailed and understandable answer, because I'm stuck and I couldn't move on with the book for a few days now.

int index = locationCells.indexOf(userInput);
This method will return -1 if the element doesn't exist in the collection.
So if you miss, it won't hit this condition:
if (index >= 0) {
locationCells.remove(index);
}
There are still elements in this collection because you didn't remove anything...
if (locationCells.isEmpty()) {
result = "kill";
} else {
result = "hit";
}
So on a miss, the result still shows "hit."
Try this instead:
if (locationCells.isEmpty()) {
result = "kill";
} else {
result = index == -1 ? "miss" : "hit";
}
If you haven't killed the opponents ships, then you either miss all ships or you hit a single ship.

I would guess the checkYourself-Method must be like this:
public String checkYourself(String userInput) {
String result = "miss";
int index = locationCells.indexOf(userInput);
if(index >= 0) {
locationCells.remove(index);
if (locationCells.isEmpty()) {
result = "kill";
}else {
result = "hit";
}
}
System.out.println(result);
return result;
}
In it's current form the ArrayList is never empty because you insert 3 Values but only remove 1 if the user-input is in the list so .isEmpty() is never TRUE.

Java: Dividing a single array by a object element value in to 2 arrays

Edit. thank you.
I have an array of 'normal' vehicles and 'large' vehicles. I have an assignment requiring me to divide them up to contribute to a far larger app.
One array for the large vehicles, one for the normal vehicles containing all the info for each element. ArrayLists are not permitted as my instructor is teaching us fundamentals.
Sample of the array
27723 4/09/61 large 7337
28507 22-02-1983 large 7055
28558 1/05/70 normal 3518
//On button press
//recieve single item from array from main and test it
//array in main will be looped for all elements.
public String loadVehicle(Vehicle v) {
String res = Constants.OK;
boolean normBool = false;
boolean largeBool = false;
//if both arrays are full , stop the method call in the main form
if (normBool && largeBool){return Constants.ERROR;}
//if vehicle size is normal, fill the normal veh array
if(v.getSize().equals(Constants.NORMAL_SIZE))
{
for(int i = 0; i<normalVehicles.length; i++)
{
//if norm veh array element is null, add the appropriate value to it
if(normalVehicles[i] == null){normalVehicles[i] = v;}
else{normBool = true;}
}
}
//if veh size is large put it in the large veh array
else if(v.getSize().equals(Constants.LARGE_SIZE))
{
for(int iL = 0; iL<largeVehicles.length; iL++)
{
if(largeVehicles[iL] == null){largeVehicles[iL] = v;}
else{largeBool = true;}
}
}
return res;
}//end method

Seems you cannot use builtin LinkedList class too, then do this:
Add the following code in your Vehicle class:
class Vehicle(){
//YOUR OTHER PIECES OF CODES ...
private static Vehicle firstLargeVehicle;
private Vehicle nextLargeVehicle;
private int index;
public void setIndex(int index){
this.index = index;
if(index == 0) Vehicle.firstLargeVehicle = this;
}
public int getIndex(){
return index;
}
public void setNextLargeVehicle(Vehicle nextLargeVehicle){
this.nextLargeVehicle = nextLargeVehicle;
}
public Vehicle getNextLargeVehicle(){
return nextLargeVehicle;
}
public addLargeVehicle(Vehicle newVehicle){
this.nextLargeVehicle = newVehicle;
newVehicle.setIndex(index + 1);
}
public getListSize(){
Vehicle lastOne = this;
while (lastOne.getNextLargeVehicle() != null){
lastOne = lastOne.getNextLargeVehicle();
}
return lastOne.getIndex() + 1;
}
public static Vehicle[] largeVehiclesToArray(){
Vehicle[] result = new Vehicle[firstLargeVehicle.getListSize()]();
Vehicle pointer = firstLargeVehicle;
for (int counter = 0; pointer != null; counter ++){
result[counter] = pointer;
pointer = pointer.getNextLargeVehicle();
}
return result;
}
}
And in your main loop, do something like the following code:
Vehicle vehicle = null;
for(Vehicle newVehicle : allVehicles) {
if (newVehicle.isLarge()){
if (vehicle == null) {
vehicle = newVehicle;
vehicle.setIndex(0);
}else{
vehicle.addLargeVehicle(newVehicle));
}
}
}
Vehicle[] largeVehicles = Vehicle.largeVehiclesToArray();
And the same story goes for normal vehicles.
Any question ?

You can write your loops like this:
for(int i = 0; i < normalVehicles.length; i++)
{
if(normalVehicles[i] == null)
{
normalVehicles[i] = v;
break;
}
}
// if last slot isn't null then it's full
normBool = normalVehicles[normalVehicles.length-1] != null;

Error using linked list remove function. after advanced for loop breaks

I am trying to get my bet system to detect if the input numbers are duplicates. When you run the program, press 2 on the "for box" bet and follow instructions from there. The issue lies in the winlose duplicate and also for the non duplicate. I don't know how I am supposed to fix the issue.
Error stacktrace :
at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:966)
at java.util.LinkedList$ListItr.next(LinkedList.java:888)
at numbersgame.Test.winLoseBetDuplicate(NumbersGame.java:190)
at numbersgame.Test.checkDuplicate(NumbersGame.java:167)
at numbersgame.Test.WinLoseBox(NumbersGame.java:134)
at numbersgame.Test.getValues(NumbersGame.java:117)
at numbersgame.NumbersGame.main(NumbersGame.java:24)
C:\Users\cymmm1\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 6 seconds)
Code :
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package numbersgame;
import java.lang.reflect.Array;
import java.util.LinkedList;
import java.util.List;
import javax.swing.JOptionPane;
/**
*
* #author cymmm1
*/
public class NumbersGame {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
Test numbers = new Test();
numbers.getValues();
boolean win = numbers.win; //this checks if you won, either as a duplicate or not.
if (win) {
System.out.println("You won");
switch (numbers.bet_Type) {
case 1:
System.out.println("You waged " + numbers.bet_Amount
+ "dollars and you will get "
+ numbers.bet_Amount * 600 + " back.");
break;
case 2:
if (numbers.dupwin) {
System.out.println("You waged " + numbers.bet_Amount
+ "dollars and you will get "
+ numbers.bet_Amount * 200 + " back.");
} else {
System.out.println("You waged " + numbers.bet_Amount
+ "dollars and you will get "
+ numbers.bet_Amount * 100 + " back.");
}
break;
}
} else {
System.out.println("Sorry, you lost $" + numbers.bet_Amount + " dollars");
}
System.exit(0);
}
}
class Test {
public int bet_Type;
public int bet_Amount;
public int player_Number;
public int winning_Number;
private JOptionPane panel;
public boolean win;
public List<Integer> digits = new LinkedList<>();
List<Integer> digits2 = new LinkedList<>();
public void getValues() {
panel = new JOptionPane();
this.bet_Type = (Integer.parseInt(panel.showInputDialog("What is the bet type. 1 for straight, 2 for box")));
this.bet_Amount = (Integer.parseInt(panel.showInputDialog("How much is the bet")));
boolean bad = true;
while (bad) {
this.player_Number = (Integer.parseInt(panel.showInputDialog("What is the player's Number. 3 numbers must be inputted")));
int playerNumCopy = this.player_Number;
while (playerNumCopy > 0) {
digits.add(0, playerNumCopy % 10);
playerNumCopy = playerNumCopy / 10;
}
int lengthOfNum = digits.size();
if (lengthOfNum != 3) {
bad = true;
} else {
bad = false;
}
}
bad = true;
while (bad) {
this.winning_Number = (Integer.parseInt(panel.showInputDialog("What is the winning Number")));
int winningnumbercopy = this.winning_Number;
while (winningnumbercopy > 0) {
digits2.add(0, winningnumbercopy % 10);
winningnumbercopy = winningnumbercopy / 10;
}
int lengthOfNum = digits2.size();
if (lengthOfNum != 3) {
bad = true;
} else {
bad = false;
}
}
//========END OF CHECK FOR PROPER NUMBERS=================================
//Now to check for type of bet and se the method appropriate
if (this.bet_Type == 1) {
win = WinLoseStraight();
} else {
win = WinLoseBox();
}
}
private boolean WinLoseStraight() {
if (this.player_Number == this.winning_Number) {
return true;
} else {
return false;
}
// this goes back to getValues
}
private boolean WinLoseBox() {
//this checks for duplicates. if it isnt a duplicate then check for a box non-dup
boolean duplicatewin = checkDuplicate();
if (duplicatewin) { //you either won with a duplicate number or nonduplicate. check Duplicate does to things at once
return true;
} else {
return false;
}
}
public boolean duplicate;
public boolean dupwin;
//this checks for duplicated numbers
public boolean checkDuplicate() {
duplicate = false;
int[] array = new int[digits.size()];
int i = 0;
for (int numbers : digits) {
array[i] = numbers;
System.out.println(array[i]);
i++;
}
for (int j = 0; j < array.length; j++) {
for (int k = j + 1; k < array.length; k++) {
if (array[k] == array[j]) {
duplicate = true;
System.out.println(array[k] + " equals " + array[j]);
break; //if duplicated found, it will exit out of the for loop
}
}
if (duplicate) {
System.out.println("we found duplicate.");
dupwin = winLoseBetDuplicate(); //if it has duplicated numbers, it will check if your numbers match up
break;
} else {
dupwin = winLostBetNonDuplicate();
}
}
return dupwin; //this will return if you have won the prize with a duplicated number. goes back to getValues
}
private boolean winLoseBetDuplicate() {
/*how this method works is we make a linked list.
use a advanced for loop and when we encounter
a hit, we remove the number from it.
if there is still a number in the linkedlist of
player number it is a lose. we still have digits as a linked list. */
//
boolean won = false;
boolean match;
for (int digitsnumbers : digits) {
System.out.println("Checking the number: " + digitsnumbers);
for (int digits2numbers : digits2) {
if (digitsnumbers == digits2numbers) {
digits.remove(digits.indexOf(digitsnumbers));
digits2.remove(digits2.indexOf(digits2numbers));
System.out.println("we found a duplicated numer match. Removing from choosing. ");
System.out.println(digits);
System.out.println(digits2);
match = true;
} else {
match = false;
}
}
}
if (digits.size() > 0) {
won = false;
} else {
won = true;
}
return won;
}
private boolean winLostBetNonDuplicate() {
boolean won;
for (int digitsnumbers : digits) {
for (int digits2numbers : digits2) {
if (digitsnumbers == digits2numbers) {
digits2.remove(digits.indexOf(digits2numbers));
digits.remove(digits.indexOf(digitsnumbers));
break;
}
}
}
if (digits.size() > 0) {
won = false;
} else {
won = true;
}
return won;
}
}

Java Binary Tree entered in a specific order

I am trying to complete an assignment where I need to write a Java program to take a string from the command line, and implement it as a Binary Tree in a specific order, then get the depth of the binary tree.
For example: "((3(4))7((5)9))"
would be entered as a tree with 7 as the root, 3 and 9 as the children, and 4 as a right child of 3, and 5 as a left child of 9.
My code is below.. The problem I am having is that, because I am basing my checks off of finding a right bracket, I am unsure how to get the elements correctly when they are not directly preceding the brackets, such as the 3 in the above string. Any direction would be greatly appreciated..
class Node {
int value;
Node left, right;
}
class BST {
public Node root;
// Add Node to Tree
public void add(int n) {
if (root == null) {
root = new Node( );
root.value = n;
}
else {
Node marker = root;
while (true) {
if (n < marker.value) {
if (marker.left == null) {
marker.left = new Node( );
marker.left.value = n;
break;
} else {
marker = marker.left;
}
} else {
if (marker.right == null) {
marker.right = new Node( );
marker.right.value = n;
break;
} else {
marker = marker.right;
}
}
}
}
} // End ADD
//Find Height of Tree
public int height(Node t) {
if (t.left == null && t.right == null) return 0;
if (t.left == null) return 1 + height(t.right);
if (t.right == null) return 1 + height(t.left);
return 1 + Math.max(height(t.left), height(t.right));
} // End HEIGHT
// Check if string contains an integer
public static boolean isInt(String s) {
try {
Integer.parseInt(s);
}
catch(NumberFormatException e) {
return false;
}
return true;
} // End ISINT
public int elementCount(String[] a) {
int count = 0;
for (int i = 0; i < a.length; i++) {
if (isInt(a[i])) count++;
}
return count;
}
} // End BST Class
public class Depth {
public static void main(String[] args) {
String[] a = args[0].split(" ");
BST tree = new BST();
int[] bcount = new int[10];
int[] elements = new int[10];
int x = 0, bracketcount = 0;
// Display entered string
System.out.print("Entered Format: ");
for (int j=0; j < a.length; j++) {
System.out.print(a[j]);
}
for (int i=0; i < a.length; i++) {
char c = a[i].charAt(0);
switch (c)
{
case '(':
bracketcount++;
break;
case ')':
if (isInt(a[i-1])) {
bcount[x] = bracketcount--;
elements[x++] = Integer.parseInt(a[i-1]);
}
break;
case '1':
case '7':
default : // Illegal character
if ( (a[i-1].charAt(0) == ')') && (a[i+1].charAt(0) == '(') ) {
bcount[x] = bracketcount;
elements[x++] = Integer.parseInt(a[i]);
}
break;
}
}
System.out.println("\nTotal elements: " + tree.elementCount(a));
// Display BracketCounts
for (int w = 0; w < x; w++) {
System.out.print(bcount[w] + " ");
}
System.out.println(" ");
// Display Elements Array
for (int w = 0; w < x; w++) {
System.out.print(elements[w] + " ");
}
System.out.println("\nDepth: " + tree.height(tree.root));
// Build the tree
for (int y = 0; y < x-1; y++) {
for (int z = 1; z < tree.height(tree.root); z++) {
if (bcount[y] == z) {
tree.add(elements[y]);
}
}
}
} // End Main Function
public static boolean isInt(String s) {
try {
Integer.parseInt(s);
}
catch(NumberFormatException e) {
return false;
}
return true;
}
} // End Depth Class

I would do a couple of statements to get access to a tree with that kind of shape:
For input string : input= "((3(4))7((5)9))"
You could do :
public class Trial {
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String input = "((3(4))7((5)9))";
String easier = input.replaceAll("\\(\\(", "");
String evenEasier = easier.replaceAll("\\)\\)", "");
System.out.println(evenEasier);
int firstVal = Integer.parseInt(evenEasier.substring(0, 1));
int firstBracketVal = Integer.parseInt(evenEasier.substring(2, 3));
int middleVal = Integer.parseInt(evenEasier.substring(3, 4));
int secondBracketVal = Integer.parseInt(evenEasier.substring(4,5));
int lastVal = Integer.parseInt(evenEasier.substring(6));
System.out.println("First Val:"+firstVal);
System.out.println("First bracket Val:"+firstBracketVal);
System.out.println("Middle Val:"+middleVal);
System.out.println("Second Bracket Val:"+secondBracketVal);
System.out.println("Last Val:"+lastVal);
}
}
This however would only ever work for entries in that specific format, if that were to change, or the length of the input goes up - this would work a bit or break.....If you need to be able to handle more complicated trees as input in this format a bit more thought would be needed on how to best handle and convert into your internal format for processing.

pseudocode:
function getNode(Node)
get one char;
if (the char is "(")
getNode(Node.left);
get one char;
end if;
Node.value = Integer(the char);
get one char;
if (the char is "(")
getNode(Node.right);
get one char;
end if;
//Now the char is ")" and useless.
end function
Before calling this function, you should get a "(" first.
In this method, the framwork of a Node in string is "[leftchild or NULL] value [rightchild or NULL])".
"("is not belong to the Node, but ")" is.