I'm trying to write a code that will count the number of occurrences of 1 string in another string. So for if the user enters "hello" and then enter "e" the code should say "There is 1 occurrence of "e". However, my current executes an infinite loop.
I've tried changing the condition on the for loop to inputEntry.equals(inputCharacter) but also had an infinite loop.
package charcounter;
import java.util.Scanner;
public class CharCounter {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
String inputEntry;
String inputCharacter;
System.out.println("Please enter a multi word string: ");
inputEntry = scnr.nextLine();
System.out.println("Enter another string: ");
inputCharacter = scnr.nextLine();
if (inputCharacter.length() == 1){
while (inputEntry.contains(inputCharacter)){
int occurrences = 0;
for(occurrences = 0;inputEntry.contains(inputCharacter); occurrences++ ){
System.out.println("There is " + occurrences + " of " + inputCharacter);
}
}
}
else{
System.out.println("Your string is too long.");
}
}
}
So for if the user enters "hello" and then enter "e" the code should say "There is 1 occurrence of "e".
The inputEntry.contains(inputCharacter) in your code always return true => endless loop
You can change to indexOf for your requirement.
int lastIndex = 0;
int count = 0;
while(lastIndex != -1){
lastIndex = inputEntry.indexOf(inputCharacter,lastIndex);
if(lastIndex != -1){
count ++;
lastIndex += inputCharacter.length();
}
}
You can change your code to
if (inputCharacter.length() == 1){
int lastIndex = 0;
int count = 0;
while(lastIndex != -1){
lastIndex = inputEntry.indexOf(inputCharacter,lastIndex);
if(lastIndex != -1){
count ++;
lastIndex += inputCharacter.length();
}
}
System.out.println("There is " + count + " of " + inputCharacter);
}
else{
System.out.println("Your string is too long.");
}
Related
I have a condition where if the user inputs a negative number or a number which is more than 100, or a string, an error message should be printed "That wasn't a valid percentage, I need a number between 0-100. Try again." and ask the user to reenter a valid number. and if the user decided to just enter, all the input should be calculated and printed the average amount.
public static void main(String[ ] args) {
int count = 0; //count to stop loop
double[ ] aGrade = new double[SIZE];
String input = new String("");
Scanner scan = new Scanner(System.in);
double total = 0;
int gTotal = aGrade.length;
boolean exit = false;
while ((count < SIZE) && (!exit)) {
System.out.print("Enter number " + (count + 1) + ": " + "\n");
try {
input = scan.nextLine();
if (Double.parseDouble(input) > 0 && Double.parseDouble(input) < 100) {
aGrade[count] = Double.parseDouble(input); //put into the array
count++; //only increment count if success
} else
System.out.println("That wasn't a valid percentage,"
+ " I need a number between 0-100. Try again.");
} catch (NumberFormatException nfe) {
exit = true; //exit loop
}
}
System.out.println("number of grades entered: " + count + "\n");
for (int i = 0; i < count; i++) {
// print entered grade
System.out.println("grade " + (i + 1) + ": " + aGrade[i]);
}
for (int i = 0; i < count; i++) {
total += aGrade[i];
}
// calculate and print the average
System.out.println("\n" + "Average grade: " + total /count);
But when I run my code, if I input letters, it won't allow the user to reinput value but prints whatever is calculated. I think it is in my if-else statement, but I am not sure how
When we try to convert String to Double it will throw java.lang.NumberFormatException. So whenever you enter String or char at that time instead of else it will go to catch block. As per your code else block only executed when user enter negative number or grater then 100 number.
I updated your code. Please review it.
import java.util.Scanner;
public class Average {
public static void main(String[] args) {
int count = 0; // count to stop loop
double[] aGrade = new double[3];
String input = new String("");
Scanner scan = new Scanner(System.in);
double total = 0;
int gTotal = aGrade.length;
boolean exit = false;
while ((count < 3) && (!exit)) {
System.out.print("Enter number " + (count + 1) + ": " + "\n");
try {
input = scan.nextLine();
if (Double.parseDouble(input) > 0 && Double.parseDouble(input) < 100) {
aGrade[count] = Double.parseDouble(input); // put into the array
count++; // only increment count if success
} else
System.out
.println("That wasn't a valid percentage," + " I need a number between 0-100. Try again.");
} catch (NumberFormatException nfe) {
nfe.printStackTrace();
exit = true; // exit loop
}
}
if (!exit) {
System.out.println("number of grades entered: " + count + "\n");
for (int i = 0; i < count; i++) {
// print entered grade
System.out.println("grade " + (i + 1) + ": " + aGrade[i]);
}
for (int i = 0; i < count; i++) {
total += aGrade[i];
}
// calculate and print the average
System.out.println("\n" + "Average grade: " + total / count);
}else {
System.out
.println("That wasn't a valid percentage," + " I need a number between 0-100. Try again.");
}
}
}
If you type letter as an input, you will never end up in your else part of the if statement since code inside if throws an exception and you are then inside catch part. Also, you wrote inside catch part, when NumberFormatException happens(when you enter letter instead of number), set exit to true and that is the reason why program don't let you type again after you input letter. Fix those things and it will work. Also, take a look at how to debug your program, learn that skill, it will help you to solve this kind of problems in the future.
Try something like this:
boolean ok = false;
try {
input = scan.nextLine();
if ("".equals(input)) {
ok = true;
exit = true;
} else if (Double.parseDouble(input) >= 0 && Double.parseDouble(input) <= 100) {
aGrade[count] = Double.parseDouble(input); //put into the array
count++; //only increment count if success
ok = true;
}
} catch (NumberFormatException nfe) {
// nothing
}
if (!ok) {
System.out.println("That wasn't a valid percentage,"
+ " I need a number between 0-100. Try again.");
}
I am trying to create a Hangman and I have 2 problems.
1) The first problem is when the user finds the word, the loop does not stop.
2) I have a variable attempts which allows to know the number of attempts. Even if the user finds the letter, the number of attempts decrease.
The word to find is no
Here is a demonstration:
1) I enter the letter n
You have 5 attempts.
--
Enter your letter : n
2) I enter the letter o
The letter is good.
You have 4 attempts.
n-
Enter your letter : o
3) Normally the loop should stop.
The letter is good.
You have 3 attempts.
no
Enter your letter :
If you have an idea thank you in advance.
Scanner input = new Scanner(System.in);
char letter = 0;
String[] words = {/*"yes",*/ "no"};
String word_random = words[(int) (Math.random() * words.length)];
boolean[] word_found = new boolean[word_random.length()];
int attempts = 5;
while(attempts > 0){
System.out.println("You have " + attempts + " attempts.");
for(int i=0; i<word_random.length(); i++) {
if ( word_found[i] ) {
System.out.print(word_random.charAt(i));
}
else {
System.out.print('-');
}
}
System.out.println("");
System.out.print("Enter your letter : ");
letter = input.next().charAt(0);
for(int i=0; i<word_random.length();i++){
if(word_random.charAt(i) == letter){
System.out.println("The letter is good. ");
word_found[i] = true;
}
}
attempts--;
}
}
}
You are just missing a checking loop or method. Check the solution below.
Scanner input = new Scanner(System.in);
char letter = 0;
String[] words = {/*"yes",*/ "no"};
String word_random = words[(int) (Math.random() * words.length)];
boolean[] word_found = new boolean[word_random.length()];
int attempts = 5;
while(attempts > 0){
System.out.println("You have " + attempts + " attempts.");
for(int i=0; i<word_random.length(); i++) {
if ( word_found[i] ) {
System.out.print(word_random.charAt(i));
}
else {
System.out.print('-');
}
}
System.out.println("");
System.out.print("Enter your letter : ");
letter = input.next().charAt(0);
for(int i=0; i<word_random.length();i++){
if(word_random.charAt(i) == letter){
System.out.println("The letter is good. ");
word_found[i] = true;
}
}
boolean done = true;
for(boolean b : word_found)
done = done && b;
if(done) break;
else attempts--;
}
I will follow to your solution, not suggest a better one.
Ad 1. Add a check if the array word found contains only true after your first for cycle and if there are only true values in the array, print "you won" and set attempts to 0
Ad 2. Move attempts-- to the else case of your first for cycle OR add attempts++ in the true case of your first for cycle
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
char letter = 0;
String[] words = { /* "yes", */ "no" };
String word_random = words[(int) (Math.random() * words.length)];
boolean[] word_found = new boolean[word_random.length()];
int attempts = 5;
while (attempts > 0) {
System.out.println("You have " + attempts + " attempts.");
for (int i = 0; i < word_random.length(); i++) {
if (word_found[i]) {
System.out.print(word_random.charAt(i));
} else {
System.out.print('-');
}
}
System.out.println("");
System.out.print("Enter your letter : ");
letter = input.next().charAt(0);
boolean match = false;
for (int i = 0; i < word_random.length(); i++) {
if (word_random.charAt(i) == letter) {
System.out.println("The letter is good. ");
word_found[i] = true;
match = true;
if (i == word_found.length - 1) {
System.out.println("THE END: attempts: " + attempts);
return;
}
}
}
if (!match) {
attempts--;
}
}
System.out.println("THE END");
}
I suggest you to modify the last part of your code like I did, and it should work.
public class Game {
public static void main(String[] args) {
String secretWord = "frog";
System.out.println("Word has " + secretWord.length() + " letters.");
System.out.println("Guess a letter: ");
int correctGuesses = 0;
int strikes = 5;
Scanner input = new Scanner(System.in);
while (strikes > 0) {
here the loop cycles through the characters in a String, and checks if the user input guessedLetter matches a char in the string. right now the loop cycles through each char starting with the first char in the string through the last, the user must guess the letters in the exact order of they are arranged in the string, how can I fix this so that any character input matching a character in the String will be correct rather than the characters having to be in order?
for (int i = 0; i < secretWord.length(); i++) {
char guessedLetter = input.next().charAt(0);
char currentLetter = secretWord.charAt(i);
if (guessedLetter == currentLetter) {
correctGuesses++;
System.out.printf("Correct Guess! %d Letters Left!\n", secretWord.length() - correctGuesses);
}
else if (guessedLetter != currentLetter) {
strikes--;
System.out.printf("Incorrect: You Have %d Chances Left..\n", strikes);
}
if (strikes == 0) {
System.out.println("You Are Out of Chances! Game over!");
}
else if (correctGuesses == secretWord.length()) {
System.out.println("You Got It! The Word is: " + secretWord);
}
}
}
}
You could try it as follows:
move all the characters of secretWord to a map (key would be the character and the value would be incidences of that character in the string).
read the character from the keyboard and interate (basically, your logic).
Here is the code.
public static void main(String[] args) {
String secretWord = "frog";
Map<Character, Integer> mapOfLetters = new HashMap<>();
for (char c : secretWord.toCharArray()) {
int count = 1;
if (mapOfLetters.containsKey(c)) {
count = mapOfLetters.get(c) + 1;
}
mapOfLetters.put(c, count);
}
System.out.println("Word has " + secretWord.length() + " letters.");
System.out.println("Guess a letter: ");
int correctGuesses = 0;
int strikes = 5;
Scanner input = new Scanner(System.in);
while (strikes > 0 && !mapOfLetters.isEmpty()) {
char guessedLetter = input.next().charAt(0);
if (mapOfLetters.containsKey(guessedLetter)) {
correctGuesses++;
System.out.printf("Correct Guess! %d Letters Left!\n", secretWord.length() - correctGuesses);
int count = mapOfLetters.get(guessedLetter) - 1;
if (count == 0) {
mapOfLetters.remove(guessedLetter);
} else {
mapOfLetters.put(guessedLetter, count);
}
} else {
strikes--;
System.out.printf("Incorrect: You Have %d Chances Left..\n", strikes);
}
}
if (strikes == 0) {
System.out.println("You Are Out of Chances! Game over!");
} else if(mapOfLetters.isEmpty()){
System.out.println("You Got It! The Word is: " + secretWord);
}
}
guessedLetter = input.next().charAt(0);
If you want to match the whole UserInput there should not be charAt(0).
On the other hand, if you just want to match any character, at first time you can test guessedLetter == currentLetter is true, then just exit program.
By the way, if you like, just google "KMP algorithm" to learn how to match String.
I have to create a program that accepts a "tweet" from a user and validates it. First it tests to make sure it is less than 140 characters.
If it is valid, it counts the number of hashtags (#), attribution symbols (#), and links ("http://) are in the string, then prints them out. My program works for hashtags and attributions, but not links. How can I fix this code so that it works?
import java.util.Scanner;
class Testing {
public static void main(String[] args) {
Scanner scan = new Scanner (System.in);
System.out.println("Please enter a tweet: ");
String input = scan.nextLine();
int length = input.length();
int count = 0;
int hashtags = 0, attributions = 0, links = 0;
char letter;
if (length > 140) {
System.out.println("Excess characters: " + (length - 140));
} else {
while (count < length) {
letter = input.charAt(count);
if (letter =='#') {
hashtags++;
count++;
}
if (letter == '#') {
attributions++;
count++;
}
if (letter == 'h') {
String test = input.substring(count,count+6);
test = test.toLowerCase();
if (test == "http://") {
links++;
count++;
} else {
count++;
}
} else {
count ++;
}
}
System.out.println("Length Correct");
System.out.println("Number of Hashtags: " + hashtags);
System.out.println("Number of Attributions: " + attributions);
System.out.println("Number of Links: " + links);
}
}
I think your code will not work with link like http://test.com/ingex.php?p=1#section. Use regular expressions instead of if () else {} if () else {}. And keep in mind: there is no token(mention, hashtag, link) which contains other token.
import java.util.Scanner;
class Testing
{
public static void main(String[] args)
{
Scanner scan = new Scanner (System.in);
System.out.println("Please enter a tweet: ");
String input = scan.nextLine();
int length = input.length();
int count = 0;
int hashtags = 0, attributions = 0, links = 0;
char letter;
if (length > 140)
{
System.out.println("Excess characters: " + (length - 140));
}
else
{
while (count < length)
{
letter = input.charAt(count);
if (letter =='#')
{
hashtags ++;
count ++;
}
if (letter == '#')
{
attributions ++;
count ++;
}
if (letter == 'h')
{
//String test = input.substring(count,count+6);
//test = test.toLowerCase();
if (input.startsWith("http://", count))
{
links ++;
count++;
}
else
{
count++;
}
}
else
{
count ++;
}
}
System.out.println("Length Correct");
System.out.println("Number of Hashtags: " + hashtags);
System.out.println("Number of Attributions: " + attributions);
System.out.println("Number of Links: " + links);
}
}
}
I changed your code in a few ways, the biggest being that instead of the == you had for checking if the links start with "http://". I also used startsWith(String s, int index) because like #Robin said, anything starting with an h would probably mess up your program.
I also used count to specify where it should start, basically the index part of you parameter
You may find additional functions and documentation in the Strings class javadoc of use.
how do i make the else statement input whether the numbers that i entered are palindrome or not? the first part works nad im just stuck in the else statement trying to figure out how to make it work. heres my code
import java.util.*;
public class Lab6
{
public static void main (String [] args)
{
String pal1, pal2="";
int choice;
Scanner in = new Scanner(System.in);
System.out.println("Word(w) or Number(n)?");
choice = in.nextLine().charAt(0);
if (choice == 'w') {
System.out.println("Enter a word: ");
pal1= in.nextLine();
int length = pal1.length();
for ( int i = length - 1 ; i >= 0 ; i-- )
pal2 = pal2 + pal1.charAt(i);
if (pal1.equals(pal2))
System.out.println("The word you entered is a palindrome.");
else
System.out.println("The word you entered is not a palindrome.");
}
else{
System.out.println("Enter a bunch of numbers: ");
pal1 = in.nextLine();
pal1 = String.valueOf(in.nextInt());
int numLength = pal1.length();
for ( int j = numLength - 1 ; j >= 0 ; j-- )
pal2 = pal2 + pal1.charAt(j);
if (pal1.equals(pal2))
System.out.println("The numbers you entered is a palindrome.");
else
System.out.println("The numbers you entered is not a palindrome.");
}
}
}
Your question is very ambiguous, if you are trying to tell the user that the string entered is NOT a palindrome, then see bellow...
Have you tried putting the if statement in brackets? you have to careful when writing if/for statement without them.
public class Lab6
{
public static void main (String [] args)
{
String pal1, pal2="";
int choice;
Scanner in = new Scanner(System.in);
System.out.println("Word(w) or Number(n)?");
choice = in.nextLine().charAt(0);
if (choice == 'w') {
System.out.println("Enter a word: ");
pal1= in.nextLine();
int length = pal1.length();
for ( int i = length - 1 ; i >= 0 ; i-- )
pal2 = pal2 + pal1.charAt(i);
if (pal1.equals(pal2)){
System.out.println("The word you entered is a palindrome.");
} else{
System.out.println("The word you entered is not a palindrome.");
}
}
else{
System.out.println("Enter a bunch of numbers: ");
pal1 = in.nextLine();
pal1 = String.valueOf(in.nextInt());
int numLength = pal1.length();
for ( int j = numLength - 1 ; j >= 0 ; j-- )
pal2 = pal2 + pal1.charAt(j);
if (pal1.equals(pal2))
System.out.println("The numbers you entered is a palindrome.");
else
System.out.println("The numbers you entered is not a palindrome.");
}
}
}
Good luck with your lab ;)
Also something like this might be more efficient:
boolean isPal(String input) {
// go through half the string length
for (int i = 0; i < input.length() / 2; i++) {
// match first half to second half (regardless if odd or even)
// -1 because strings starta at a 0 index
if (input.charAt(i) != input.charAt(input.length() - 1 - i)) {
return false;
}
}
return true;
}