Array index out of bounds exception 4 [duplicate] - java

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What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?
(26 answers)
Closed 6 years ago.
I keep getting an error when trying to delete or display the users that I've created. Pointing to the line of code where it actually does the deletion or displaying of a certain user. I can't seem to figure out where the error is coming from.
import java.util.*;
public class contactInfo {
public static void main(String[] args) {
String tracker[][] = {
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",},
{" ", " ", " ", " ",}
};
Scanner input = new Scanner(System.in);
int picker = 0;
while (true) {
System.out.print("Please choose an option: \n 1. Add a user \n 2. Delete a user \n 3. Display a user \n 4. Quit ");
picker = input.nextInt();
if (picker == 1) {
addUser(tracker);
} else if (picker == 2) {
deleteUser(tracker);
} else if (picker == 3) {
displayUser(tracker);
} else {
break;
}
}
}
public static String[][] addUser(String[][] add) {
Scanner input = new Scanner(System.in);
System.out.print("Which user is this information for (1 - 10): ");
int user = input.nextInt();
System.out.println(" ");
System.out.print("Enter the users first name: ");
add[user][0] = input.next();
System.out.println(" ");
System.out.print("Enter the users last name: ");
add[user][1] = input.next();
System.out.println(" ");
System.out.print("Enter the users phone number (without dashes): ");
add[user][2] = input.next();
System.out.println(" ");
System.out.print("Enter the users age: ");
add[user][3] = input.next();
System.out.println(" ");
return add;
}
public static String[][] deleteUser(String[][] del) {
Scanner input = new Scanner(System.in);
System.out.print("Which user would you like to delete?: ");
int user = input.nextInt();
for (int i = 0; i < del.length - 1; i++) {
del[user][i] = " ";
}
return del;
}
public static String[][] displayUser(String[][] displ) {
Scanner input = new Scanner(System.in);
System.out.print("Which user would you like to display?: ");
int user = input.nextInt();
for (int i = 0; i < displ.length; i++) {
System.out.print(displ[user][i] + " ");
}
return displ;
}
}


Your tracker is a 2-dimensional array. 10 rows of 4 strings each. The problem is this code:
for (int i = 0; i < del.length - 1; i++)
{
del[user][i] = " ";
}
You iterate over the array of 4 strings, but the variable i will go from 0 to 8. What you want is something like:
for (int i = 0; i < del[user].length; i++)
{
del[user][i] = " ";
}


Instead of using displ.length or del.length for you limits, use displ[user].length or del[user].length.

Related

How to prompt user to enter which [row][column]

I want the user to enter which row and which column in order to read the data in it
for example if the user enter row = 6 column = 0, it will print out Pw1
static String fullChessBoard[][] = {
{"Rb1", "Kb1", "Bb1", "Qb1", "Ab1", "Bb2", "Kb2", "Rb2"},
{"Pb1", "Pb2", "Pb3", "Pb4", "Pb5", "Pb6", "Pb7", "Pb8"},
{" ", " ", " ", " ", " ", " ", " ", " "},
{" ", " ", " ", " ", " ", " ", " ", " "},
{" ", " ", " ", " ", " ", " ", " ", " "},
{" ", " ", " ", " ", " ", " ", " ", " "},
{"Pw1", "Pw2", "Pw3", "Pw4", "Pw5", "Pw6", "Pw7", "Pw8"},
{"Rw1", "Kw1", "Bw1", "Qw1", "Aw1", "Bw2", "Kw2", "Rw2"},
};
System.out.println(Player1W + ", please make a move");
int row = scan.nextInt();
int column = scan.nextInt();

Try this code
import java.util.Scanner;
public class HelloChess{
static String fullChessBoard[][] = {
{"Rb1", "Kb1", "Bb1", "Qb1", "Ab1", "Bb2", "Kb2", "Rb2"},
{"Pb1", "Pb2", "Pb3", "Pb4", "Pb5", "Pb6", "Pb7", "Pb8"},
{" ", " ", " ", " ", " ", " ", " ", " "},
{" ", " ", " ", " ", " ", " ", " ", " "},
{" ", " ", " ", " ", " ", " ", " ", " "},
{" ", " ", " ", " ", " ", " ", " ", " "},
{"Pw1", "Pw2", "Pw3", "Pw4", "Pw5", "Pw6", "Pw7", "Pw8"},
{"Rw1", "Kw1", "Bw1", "Qw1", "Aw1", "Bw2", "Kw2", "Rw2"},
};
public static void main(String []args){
Scanner scan = new Scanner(System.in);
System.out.print("Enter Row: ");
int row = scan.nextInt();
System.out.print("Enter Column: ");
int column = scan.nextInt();
System.out.println("Result : "+fullChessBoard[row][column]);
scan.close();
}
}

I'm assuming this program you are writing is a command line program, where the user puts information into the command prompt and your program responds. If it's not, please let me know, as my answer operates under that assumption.
There's more than one way to get input from the command line in Java. The following link has a few great examples:
[https://www.geeksforgeeks.org/ways-to-read-input-from-console-in-java/][1]
Here's a quick example I chalked up that outputs the first repeated letter from a string the user enters, it uses the BufferedReader class set to get input from the System.in object wrapped by an InputStreamReader. I'm sure that sounds complicated, but the code explains it better:
import java.io.BufferedReader;
import java.io.Console;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Set;
import java.util.TreeSet;
public class FirstRecurringCharacter {
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter your string: ");
String toAnalyze = reader.readLine();
returnFirstRecurring(toAnalyze);
}
private static Character returnFirstRecurring(String toAnalyze) {
String toSearch = toAnalyze;
Set<Character> seenCharacters = new TreeSet<>();
for (int i = 0; i < toSearch.length(); i++) {
if (seenCharacters.contains(toSearch.charAt(i))) {
System.out.println(toSearch.charAt(i));
return toSearch.charAt(i);
} else {
seenCharacters.add(toSearch.charAt(i));
}
}
System.out.println("No repeating characters.");
return null;
}
}
The .readLine() method gets the users input after they hit enter on the console. Try it yourself!
With your program, you might want to prompt them, one at a time, to insert a row index, then a column index, you can cast their input to integers if needed, and then use them in the remainder of the program. I hope this helps!

same string in multiple while loops not resolved

The logic I'm trying to construct is when the user collects four total affiliates, the console will print that they've reached four but they can still go on if they choose to.
If they decide to stop at four, they should type "quit". The problem rises at the second while loop with the if else statements. I get the error "aff cannot be resolved".
import java.util.Scanner;
public class Seption {
public static void main(String[] args) {
System.out.println("Welcome back!");
Scanner userName = new Scanner(System.in);
System.out.println("Username: ");
String username = userName.next();
Scanner passWord = new Scanner(System.in);
System.out.println("Password: ");
String password = passWord.next();
int affCount = 0;
while (affCount <= 4) {
Scanner newAff = new Scanner(System.in);
System.out.println("enter new affiliate");
String aff = newAff.nextLine();
System.out.println("Alright, " + aff + " is now your new affiliate!");
affCount = affCount + 1;
System.out.println("You now have " + affCount + " affiliates");
if (affCount == 4) {
System.out.println("Congratulations! You've accumulated 4 affiliates!"
+ " any new affiliates added to this branch will be extra earnings"
+ " You can also make a new branch and start over"
+ " To quit this branch, Type 'quit'");
continue;
}
}
while (affCount > 4) {
if (aff.equals("quit") == false) {
Scanner newAff = new Scanner(System.in);
System.out.println("enter new affiliate");
String aff = newAff.nextLine();
System.out.println("Alright, " + aff + " is now your new affiliate!");
affCount = affCount + 1;
System.out.println("You now have " + affCount + " affiliates");
}
else if (aff.equals("quit")) {
System.out.println("This branch is now over");
break;
}
}
}
}

You should just create an instance of the Scanner from System.in once and use that same instance anywhere that you need to get an input from the user:
public static void main(String[] args){
System.out.println("Welcome back!");
Scanner scanner = new Scanner(System.in);
System.out.println("Username: "); String
username = scanner.next();
System.out.println("Password: ");
String password = scanner.next();
int affCount = 0;
String aff = "";
while (affCount <= 4) {
System.out.println("enter new affiliate");
aff = scanner.nextLine();
System.out.println("Alright, " + aff + " is now your new affiliate!");
affCount = affCount + 1;
System.out.println("You now have " + affCount + " affiliates");
if (affCount == 4)
{
System.out.println("Congratulations! You've accumulated 4 affiliates!" + " any new affiliates added to this branch will be extra earnings" + " You can also make a new branch and start over" + " To quit this branch, Type 'quit'");
continue;
}
}
while (affCount > 4) {
if (aff.equals("quit") == false)
{
System.out.println("enter new affiliate");
aff = scanner.nextLine();
System.out.println("Alright, " + aff + " is now your new affiliate!");
affCount = affCount + 1;
System.out.println("You now have " + affCount + " affiliates");
}
else if (aff.equals("quit"))
{
System.out.println("This branch is now over");
break; }
}
}

How can I format the output with System.out?

I am creating a Premier League football table in my spare time and I have come across a problem. While the program runs I want it to be perfect and output in the format I want it to, the problem is:
You enter the the Input (" HomeTeam : AwayTeam : HomeScore : AwayScore ") as follows
When you are done with the list you enter "quit" to stop the program
My issue is that the scores come out like this
(" HomeTeam | AwayTeam | HomeScore | AwayScore ")
I intend it to print like this (" HomeTeam [HomeScore] | AwayTeam [AwayScore] ")
I have tried many variations of System.out.printlns to no avail, even trying to make several Boolean conditions that will output the input in the way I want it too. I am truly at a loss and it is frustrating - I hope that someone can give me tips the code is attached
Edited for loop;
for (int i = 0; i < counter; i++) { // A loop
String[] words = product_list[i].split(":");
System.out.println(words[0].trim() + "[" + words[2].trim() + "]" + " | " + words[1].trim() + "[" + words[3].trim()) + "]";

This should work:
Scanner sc = new Scanner(System.in);
public void outputScore(String input) {
String[] words = input.trim().split("\\s+");
String satisfied = sc.nextLine();
if (satisfied.equals("quit")) {
System.out.println(words[0] + " [" + words[4] + "] | " + words[2] + " [" + words[6] + "]");
}
}
This is what the method should look like when you call it:
outputScore(sc.nextLine());
Here is the code to your edited question:
String [] product_list = new String [100];
int counter = 0;
Scanner scanner = new Scanner(System.in);
System.out.println("Input as follows:");
System.out.println("Home team : Away team : Home score : Away score");
String line = null;
while (!(line = scanner.nextLine()).equals("")) {
if (line.equals("quit")) {
break;
} else {
product_list[counter] = line;
System.out.println("Home team : Away team : Home score : Away score");
}
counter++;
}
for (int i = 0; i < counter; i++) {
String[] words = product_list[i].split(":");
System.out.println(words[0].trim() + " : " + words[2].trim() + " | " + words[1].trim() + " : " + words[3].trim());
}
Hope this helps.

I have 2 errors compiling my java Lottery program using arrays

import java.util.Random;
import java.util.Scanner;
public class LotteryGame{
public static void main(String[] args) {
int NUM_DIGITS = 6;
int[] userDigits = new int[NUM_DIGITS];
int[] lotteryNumbers = new int[NUM_DIGITS];
int sameNum;
generateNumbers(lotteryNumbers);
getUserData(userDigits);
sameNum = compareArrays(lotteryNumbers, userDigits);
System.out.println("Winning numbers: " + lotteryNumbers[0] + " "
+ lotteryNumbers[1] + " " + lotteryNumbers[2] + " "
+ lotteryNumbers[3] + " " + lotteryNumbers[4] + " " + lotteryNumbers[5] + " ");
System.out.println("Your numbers: " + userDigits[0] + " "
+ userDigits[1] + " " + userDigits[2] + " " + userDigits[3]
+ " " + userDigits[4] + " " + userDigits[5] +" ");
System.out.println("Number of matching digits: " + sameNum);
if (sameNum == 6) {
System.out.println("First prize!!!");
}
if (sameNum == 5) {
System.out.println("Second prize!!!");
}
if (sameNum == 0) {
System.out.println("No matching numbers, you lost.");
}
}
public static void generateNumbers(int[] lotteryNumbers) {
Random randNum = new Random();
lotteryNumbers[0] = randNum.nextInt(59);
lotteryNumbers[1] = randNum.nextInt(59);
lotteryNumbers[2] = randNum.nextInt(59);
lotteryNumbers[3] = randNum.nextInt(59);
lotteryNumbers[4] = randNum.nextInt(59);
lotteryNumbers[5] = randNum.nextInt(59);
return lotteryNumbers[5];
}
public static void getUserData(int[] userDigits) {
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter first digit: ");
userDigits[0] = keyboard.nextInt();
System.out.print("Enter second digit: ");
userDigits[1] = keyboard.nextInt();
System.out.print("Enter third digit: ");
userDigits[2] = keyboard.nextInt();
System.out.print("Enter fourth digit: ");
userDigits[3] = keyboard.nextInt();
System.out.print("Enter fifth digit: ");
userDigits[4] = keyboard.nextInt();
System.out.print("Enter sixth digit: ");
userDigits[5] = keyboard.nextInt();
return userDigits[5];
}
public static int compareArrays(int[] userDigits, int[] lotteryNumbers) {
int sameNum = 0;
for (int i = 0; i < 6; i++) {
for (int x = 0; x < 5; x++) {
if (lotteryNumbers[i] == userDigits[x]) {
sameNum++;
}
}
}
return sameNum;
}
}
When I compile I get the following errors-
LotteryGame.java:51: error: incompatible types: unexpected return value
return lotteryNumbers[5];
^
LotteryGame.java:72: error: incompatible types: unexpected return value
return userDigits[5];
^
2 errors
Can any of you help me with these compilation errors? I'm trying to get this to work. The user is supposed to input 6 numbers, and the program is supposed to pick randomly 6 numbers. Using these numbers, the program will compare the numbers with echoed input.

generateNumbers and getUserData are void functions, meaning they don't return anything, so you can't return anything from them.
You probably want to declare them as functions returning int instead:
public static int generateNumbers(int[] lotteryNumbers)

Univerio is correct in answering your original question.
Looking at your test code you might consider removing the return statement on those two functions since you are just populating both arrays.

How do I make this if statement?

Apologies for the silly question, I am currently struggling to learn java. I need this code to work so that it will repeat unless '0' is entered for the studentNumber, I'm unsure of how to get the "please enter student number" part to work when I have to declare the int for that before the if statement? I'm not sure if I've approached this completely wrong or what, but I need to be able to repeat the data entry unless "0" is entered as the studentNumber. Thanks for any help!
class Main {
public static void main( String args[] ) {
int studentNumber = BIO.getInt();
if(studentNumber > 0) {
System.out.print("#Please enter the student number : ");
System.out.print("#Please enter the coursework mark : ");
int courseWork = BIO.getInt();
System.out.print("#Please enter the exam mark : ");
int examMark = BIO.getInt();
double average = (double)(courseWork + examMark) / 2;
System.out.printf("sn = " + studentNumber
+ " ex = " + examMark + " cw = " + courseWork
+ " mark = " + average);
} else {
System.out.print("#End of data");
}
}
}
}

Use while()
while(studentNumber > 0){
studentNumber = BIO.getInt();
.........
........
}
See also
while in Java

Use while() instead of if, along with the following changes:
System.out.print("#Please enter the student number : ");
int studentNumber = BIO.getInt();
while(studentNumber > 0) {
System.out.print("#Please enter the coursework mark : ");
int courseWork = BIO.getInt();
System.out.print("#Please enter the exam mark : ");
int examMark = BIO.getInt();
double average = (double)(courseWork + examMark) / 2;
System.out.printf("sn = " + studentNumber
+ " ex = " + examMark + " cw = " + courseWork
+ " mark = " + average);
System.out.print("#Please enter the student number : ");
studentNumber = BIO.getInt();
}
System.out.print("#End of data");
This, as opposed to the other answers, will ensure that even in the first iteration, you perform the check (and promt the user for the student number).

Using Scanner to get the input from the user and process the input value
import java.util.Scanner;
public class ConditionCheck {
public static void main(String[] args) {
Scanner BIO = new Scanner(System.in);
System.out.print("#Please enter the student number : ");
int studentNumber = BIO.nextInt();
if(studentNumber > 0) {
System.out.print("#Please enter the coursework mark : ");
int courseWork = BIO.nextInt();
System.out.print("#Please enter the exam mark : ");
int examMark = BIO.nextInt();
double average = (double)(courseWork + examMark) / 2;
System.out.printf("sn = " + studentNumber
+ " ex = " + examMark + " cw = " + courseWork
+ " mark = " + average);
} else {
System.out.print("#End of data");
}
}
}

You should be using a while statement and do something as below:
class Main
{
public static void main( String args[] )
{
int studentNumber = 1;
While(studentNumber > 0)
{
studentNumber = BIO.getInt();
System.out.print("#Please enter the student number : ");
System.out.print("#Please enter the coursework mark : ");
int courseWork = BIO.getInt();
System.out.print("#Please enter the exam mark : ");
int examMark = BIO.getInt();
double average = (double)(courseWork + examMark) / 2;
System.out.printf("sn = " + studentNumber + " ex = " + examMark + " cw = " + courseWork + " mark = " + average);
}
else
{
System.out.print("#End of data");
}
}
}

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