I'm trying to write my own Java word count program. I know there may already be a method for this, but I'd like to get it work. I'm getting an out of bounds error at line 14. I'm trying to use an input word to count how many times it appears in an input string. So I'm looping up to stringlength - wordlength, but that's where the problem is.
Here is the code:
import java.util.Scanner;
public class wordcount {
public static void main(String[] args)
{
Scanner s = new Scanner(System.in);
System.out.print( "Enter word : " );
String word = s.nextLine();
Scanner t = new Scanner(System.in);
System.out.print("Enter string: ");
String string = t.nextLine();
int count = 0;
for (int i = 0; i < string.length()-word.length(); i = i+1){
String substring = string.substring(i,i+word.length());
if (match(substring, word)==true){
count += 1;
}
}
System.out.println("There are "+count+ " repetitions of the word "+word);
}
public static boolean match(String string1, String string2){
for (int i=0; i<string1.length(); i+=1){
if (string1.charAt(i)!=string2.charAt(i)){
return false;
}
}
return true;
}
}
First of all, two Scanners are not necessary, you can do many inputs with the same Scanner object.
Also, this if condition
if (match(substring, word) == true)
can be rewritten like
if (math(substring, word))
I would also recommend you to use i++ to increase the loop variable. Is not strictly necessary but is "almost" a convention. You can read more about that here.
Now, about theIndexOutOfBoundsException, I've tested the code and I don't find any input samples to get it.
Besides, there is an issue, you are missing one iteration in the for:
for (int i = 0; i < string.length() - word.length() + 1; i++) { // Add '+ 1'
String substring = string.substring(i, i + word.length());
// System.out.println(substring);
if (match(substring, word)) {
count++;
}
}
You can test it by putting a print statement inside the loop, to print each substring.
I'm not getting an out of bounds error, can you tell me what values you were using for word and string?
I have identified a bug with your program. If word is equal to string, it still returns count 0. I suggest adding one more iteration and using regionMatches instead. RegionMatches makes your match method obsolete and will return false if word.length() + i is equal or greater than string.length(), avoiding out of bounds issues.
As you can see I also moved the calculations to a seperate method, this will make your code more readable and testable.
And as Christian pointed out; you indeed do only need one Scanner object. I've adapted the code below to reflect it.
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter word : ");
String word = sc.nextLine();
System.out.print("Enter string: ");
String string = sc.nextLine();
int count = calculateWordCount(word, string);
System.out.println("There are " + count + " repetitions of the word " + word);
}
private static int calculateWordCount(String word, String string) {
int count = 0;
for (int i = 0; i < string.length() - word.length() + 1; i++) {
if (word.regionMatches(0, string, i, word.length())) {
count++;
}
}
return count;
}
Related
The following Java program is supposed to manipulate a string input by the user in such a way that the user will decide which character needs to be replaced with another and just the last character from the string should be replaced. Example if the user enters the string "OYOVESTER" and decides to replace "O" with "L", the program should output the following result: "OYLVESTER" (notice that only the last "O" was replaced with "L")
NOTE: YOU CANNOT USE BREAK COMMAND TO STOP THE LOOP. IT IS PROHIBITED.
import java.util.Scanner;
public class StringFun {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter the string to be manipulated");
String inString = keyboard.nextLine();
String outString = "";
//Replace Last
System.out.println("Enter the character to replace");
char oldCharF = keyboard.next().charAt(0);
System.out.println("Enter the new character");
char newCharF = keyboard.next().charAt(0);
int count = 0; // variable that tracks number of letter occurrences
for(int index = inString.length() - 1;index >= 0;index--) {
if(inString.charAt(index) == oldCharF && count < 1){
outString = newCharF + outString;
outString = outString + inString.substring(0,index);
count++;
}
if (count < 1) {
outString = outString + inString.charAt(index);
}
}
System.out.print("The new sentence is: "+outString);
}
}
I keep getting the following output which is incorrect:
Enter the string to be manipulated
OYOVESTER
Enter the character to replace
O
Enter the new character
L
The new sentence is: LRETSEVOY
There are many simpler ways to achieve your requirement but I hope you have to demonstrate this with loops (without breaks)
Then you can use some thing like this :
boolean skip = false;
for (int index = inString.length() - 1; index >= 0; index--) {
if (!skip && inString.charAt(index) == oldCharF) {
outString = newCharF + outString;
skip = true;
}
else {
outString = inString.charAt(index) + outString;
}
}
PS : Using String concatenation inside loops is not recommended since
every String concatenation copies the whole String, usually it is preferable to
replace it with explicit calls to StringBuilder.append() or StringBuffer.append()
No break command seems like a weird condition. You could just a boolean value, and other methods, to break the loop when you need. Why not do something like this?
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter the string to be manipulated");
String word = keyboard.nextLine();
//Replace Last
System.out.println("Enter the character to replace");
char oldCharF = keyboard.next().charAt(0);
System.out.println("Enter the new character");
char newCharF = keyboard.next().charAt(0);
int index = word.lastIndexOf(oldCharF);
if(index > 1){
word = word.substring(0,index) + newCharF + word.substring(index+1);
}
System.out.println("The new sentence is: " + word);
}
I have created a palindorme java program which is getting an error.the error is saying int cannot be converted to boolean.
import java.util.Scanner;
public class palindrome
{
public static void main()
{
Scanner sc = new Scanner(System.in);
int l,i;
String s,s1;
System.out.println("Enter your string");
s = sc.nextLine();
l = s.length();
for(i=0;l-i-1;i++)
{
s1 = s + s.charAt(i);
}
if(s1==s)
System.out.println("This is Palindrome");
else
System.out.println("This is not a Palindrome");
}
}
For loop condition seems wrong.
for(initial counter; condition to terminate; increase counter) {}
for(i=0; i<l; i++) {}
Along with the answer above you can try a different approach. You don't need to go all the string length to check a palindrome. A palindrome can be checked iterating half of the array length like this -
public void checkPalindrome(String strToCheck){
char[] arr = strToCheck.toCharArray();
int size = arr.length;
char [] original = Arrays.copyOf(arr,arr.length);
for (int i = 0; i < size / 2; i++) {
char temp = arr[i];
arr[i] = arr[size-i-1];
arr[size-i-1] = temp;
}
if(Arrays.equals(arr, original)) {
System.out.println("Palindrome");
} else {
System.out.println("Not a palindrome");
}
}
What are done here:
reversing the string first iterating the halfway
comparing the reversed string with the original using Arrays.equals() method.
There are quite a few things off here, first here is the fixed code:
public static void main(String [] args)
{
Scanner sc = new Scanner(System.in);
int l,i;
String s = "",s1 = "";
System.out.println("Enter your string");
s = sc.nextLine();
l = s.length();
for(i = l - 1; i >= 0; i--)
{
s1 = s1 + s.charAt(i);
}
if(s1.equals(s))
System.out.println("This is Palindrome");
else
System.out.println("This is not a Palindrome");
}
The first thing to fix was your for loop, as you saw you were getting an error. This was fixed by setting the initial i to the length minus 1, changing the loop condition to i >= 0, and using i-- to subtract 1 from i each loop.
These changes to the loop were made so that the character starting from the last position in the String is the first one being return by s.charAt(i) so you can reverse the String. I think you were attempting to do something along these lines to add the characters starting from the end to a String.
I also changed s1 = s + s.charAt(i) to s1 = s1 + s.charAt() so the correct String is being appended. (This should probably be StringBuilder however).
s and s1 now have the initial condition of "" instead of nothing.
And finally you cannot compare String equality with ==, it must be s1.equals(s).
Test Run:
Enter your string
racecar
This is Palindrome
I have an assignment due two days and I have been trying a lot of days to do this, but I am burned, tried to come back to it, still no progress.
THE ASSIGNMENT is the following:
Java program that computes the above statistics from
any text file. Here’s what it might look like in action:
Name of the input file: example.txt
The proportion of 1-letter words: 3.91% (74 words)
The proportion of 2-letter words: 18.52% (349 words)
The proportion of 3-letter words: 24.24% (456 words)
The proportion of 4-letter words: 19.80% (374 words)
The proportion of 5-letter words: 11.33% (212 words)
…
…
The proportion of 12-letter words: 0.45% (8 words)
Proportion of 13- (or more) letter words: 0.51% (9 words)
Now In order to do this, I thought to divide my program into three methods: Read the method, count the letters and distinguish them and finally display it as the example above. Now that I said that, here is my code right now:
/*like make smaller functions
where each function has one task
like to loop through the file and return an array of words
then use that as input to another function whose purpose is to count the
letters
and then pass that array into a function for printing that.
*/
import java.io.*;
import java.util.Scanner;
class Autorship {
public static void main(String[] args) {
try {
System.out.println("Name of input file: ");
Scanner sc1 = new Scanner(System. in );
sc1.useDelimiter("[^a-zA-Z]");
String fname = sc1.nextLine();
sc1.close();
sc1 = new Scanner(new FileReader(fname));
sc1.useDelimiter("[^a-zA-Z]");
String line;
System.out.println(WordCount(fname, sc1));
} catch (FileNotFoundException e) {
System.out.println("There was an error opening one of the files.");
}
}
public static int WordCount(String fname, Scanner sc1) {
int wordCount = 0;
int lineCount = 0;
while (sc1.hasNextLine()) {
String line;
line = sc1.nextLine();
lineCount++;
String[] strings = line.split(" ");
int[] counts = new int[14];
for (String str: strings)
if (str.length() < counts.length) counts[str.length()] += 1;
System.out.println("This is counts length: " + counts.length);
for (int i = 1; i < counts.length; i++)
System.out.println(i + " letter words: " + counts[i]);
}
return 0;
}
}
Now please I do not want the answer, as that would be plagiarism, and I am not that kind of person, I just want a bit of help to continue to progress, I'm so stuck right now, thanks ^^
Here is an adjusted and working version. I commented the lines I edited.
Your code wasn't that bad and it was working quite well. The only problem you had was that you've printed out the letter counts inside the while-loop instead of doing it outside. Therefore it repeated with every new line that was read from the file.
Please note: I strongly recommend to always use curly brackets even though Java syntax allows to not use them with if-statements and for-loops if they're followed by only one line of code to execute. But not using them makes the code harder to read and error prone.
public static void main(String[] args) {
try {
System.out.println("Name of input file: ");
Scanner sc1 = new Scanner(System. in );
sc1.useDelimiter("[^a-zA-Z]");
String fname = sc1.nextLine();
sc1.close();
sc1 = new Scanner(new FileReader(fname));
sc1.useDelimiter("[^a-zA-Z]");
String line;
System.out.println("WordCount: " + WordCount(fname, sc1)); // edited
} catch (FileNotFoundException e) {
System.out.println("There was an error opening one of the files.");
}
}
public static int WordCount(String fname, Scanner sc1) {
int wordCount = 0;
int lineCount = 0;
final int MAXIMUM_LENGTH = 14; // edited. Better use a constant here.
int[] counts = new int[MAXIMUM_LENGTH]; // edited. Constant applied
while (sc1.hasNextLine()) {
String line = sc1.nextLine();
// increment line count
lineCount++;
String[] strings = line.split(" ");
// increment word count
wordCount += strings.length; // added
// edited. curly brackets and constant MAXIMUM_LENGTH
for (String str: strings) {
if (str.length() < MAXIMUM_LENGTH) {
counts[str.length()] += 1;
}
}
}
// edited / added. finally show the results
System.out.println("maximum length: " + MAXIMUM_LENGTH);
System.out.println("line count: " + lineCount);
System.out.println("word count: " + wordCount);
// edited. moved out of the while-loop. MAXIMUM_LENGTH applied.
for (int i = 1; i < MAXIMUM_LENGTH; i++) {
System.out.println(i + " letter words: " + counts[i]);
}
// edited.
return wordCount;
}
I am a student at the moment so I am still learning. I picked up VB pretty quick and it was simple Java on the other hand I am pretty confused on.
The Assignment I have been given this time has me confused "Write a method to determine the number of positions that two strings differ by. For Example,"Peace" and "Piece" differ in two positions. The method is declared int compare(String word1, String word2); if the strings are identical, the method returns 0. It returns -1 if the two strings have different lengths."
Additional "Write a main method to test the method. The main method should tell how many, positions the strings differ, or that they are identical, or if they are different lengths, state the lengths. Get the strings from the console.
So far this is where I am at and I am looking for someone to help break this down in I DUMDUM terms if they can I don't need a solution only help understanding it.
package arraysandstrings;
import java.util.Scanner;
public class differStrings {
public static void main (String agrs[]){
Scanner scanner = new Scanner (System.in);
System.out.print("Enter a word");
String word1;
String word2;
word1 = scanner.next();
System.out.print("Enter another word");
word2 = scanner.next();
int count = 0;
int length = word1.length();
for(int x = 0; x >= length; x = x+1) {
if (word1.charAt(x) == word2.charAt(x)) {
count = count + 1;
System.out.print (count);
}
}
}
}
Additional Question
package arraysandstrings;
import java.util.Scanner;
public class differStrings {
public static void main (String agrs[]){
Scanner scanner = new Scanner (System.in);
System.out.println("Enter a word");
String word1 = scanner.next();
System.out.println("Enter another word");
String word2 = scanner.next();
int count = 0;
int word1Length = word1.length();
int word2Length = word2.length();
if (word1Length != word2Length) {
System.out.println ("Words are a diffrent length");
System.out.println (word1 + "Has" + word1.length() + " chars");
System.out.println (word2 + "Has" + word2.length() + " chars");
}
for(int x = 0; x < word1Length; x = x+1) {
if (word1.charAt(x) != word2.charAt(x)) {
count = count + 1;
}}}
System.out.println (count+" different chars");
}
After implementing the knowledge Iv gained from your responses I have ran in to a problem with the last line:
System.out.println (count+" different chars");
It says Error expected however it worked before I added the next part of my assignment which was this:
if (word1Length != word2Length) {
System.out.println ("Words are a diffrent length");
System.out.println (word1 + "Has" + word1.length() + " chars");
System.out.println (word2 + "Has" + word2.length() + " chars");
}
for(int x = 0; x >= length; x = x+1) {
You probably mean
for(int x = 0; x < length; x = x+1) {
Shifting around some code, adding some line breaks and making 2 small tweaks to the logic produces a program that is closer to what you are trying to build.
package arraysandstrings;
import java.util.Scanner;
public class differStrings {
public static void main (String agrs[]){
Scanner scanner = new Scanner (System.in);
System.out.println("Enter a word");
String word1 = scanner.next();
System.out.println("Enter another word");
String word2 = scanner.next();
int count = 0;
int length = word1.length();
for(int x = 0; x < length; x = x+1) {
if (word1.charAt(x) != word2.charAt(x)) {
count = count + 1;
}
}
System.out.println (count+" different chars");
}
}
It looks like in addition to the for loop that #LouisWasserman pointed out you had code that was trying to find characters that are the same.
What you need is a loop which compares the two strings and counts the places where they are not equal.
Your logic counts the number of places where the two characters are the same. You are also printing the count each time the two characters are equal.
What it sounds like you need is a loop that iterates over the characters in the two strings comparing each character and incrementing the count of mis-matched or different characters. Then after getting a count of different characters by comparing all of the characters, you would print out the count of different characters.
So the basics would be: (1) read each of the strings, (2) check that the lengths are the same, (3) if same length then loop over the string comparing each character and incrementing the count of mis-matched characters each time there is a difference, (4) print out the count. If the string lengths are different then just set the count to negative one (-1) and do not bother to compare the two strings.
What would be kind of neat to do is to create a string of underscores and asterisk, in which each matching character position is represented by an underscore and each mis-matching character position is represented by an asterisk or perhaps the string would contain all of the matching characters and the mis-matching characters would be replaced by an asterisk.
Edit: adding example program
The example below is an annotated rewrite of your program. One change that I made was to use a function to perform the counting of the non-matching characters. The function, countNonMatchChars () is a static function in order to work around the object oriented nature of Java. This function is a utility type function and not really part of a class. It should be available to anyone who wants to use it.
Also rather than incrementing variables with the syntax of var = var + 1; I instead use the postincrement operator of ++ as in var++;.
package arraysandstrings;
import java.util.Scanner;
public class so_strings_main {
// function to compare two strings and count the number
// of characters that do not match.
//
// this function returns an integer indicating the number
// of characters that did not match or a negative one if the
// strings are not equal in length.
//
// "john" "john" returns 0
// "john1" "john2" returns 1
// "mary1" "john1" returns 4
// "john" "john1" returns -1 (lengths are not equal)
public static int countNonMatchChars (String s1, String s2)
{
// initialize the count to negative one indicating strings unequal in length
// get the lengths of the two strings to see if any comparison is needed
int count = -1;
int word1Length = s1.length();
int word2Length = s2.length();
if (word1Length == word2Length) {
// the lengths of the two strings are equal so we now do our comparison
// we start count off at zero. as we find unmatched characters, we
// will increment our count. if no unmatched characters found then
// we will return a count of zero.
count = 0;
for(int iLoop = 0; iLoop < word1Length; iLoop++) {
if (s1.charAt(iLoop) != s2.charAt(iLoop)) {
// the characters at this position in the string do not match
// increment our count of non-matching characters
count++;
}
}
}
// return the count of non-matching characters we have found.
return count;
}
public static void main (String agrs[]){
Scanner scanner = new Scanner (System.in);
System.out.println("Count non-matching characters in two strings.");
System.out.println("Enter first word");
String word1 = scanner.next();
System.out.println("Enter second word");
String word2 = scanner.next();
int count = countNonMatchChars (word1, word2);
if (count < 0) {
System.out.println ("Words are a diffrent length");
System.out.println (" " + word1 + " Has " + word1.length() + " chars");
System.out.println (" " + word2 + " Has " + word2.length() + " chars");
} else {
System.out.println (count + " different chars");
}
}
}
this was the solution to my homework and the purpose was to reverse each word in a string based on user inputting a sentence. I have completed this on my own, but I'm just wondering how the iterator worked in this piece of code. I don't understand the delcaration of tempword = ""; and how he printed out each word delimited by spaces.
import java.util.Scanner;
public class StringReverser
{
public static void main(String args[])
{
String sentence;
String word;
String tempWord = "";
Scanner scan = new Scanner(System.in);
Scanner wordScan;
System.out.print("Enter a sentence: ");
sentence = scan.nextLine();
wordScan = new Scanner(sentence);
while(wordScan.hasNext())
{
word = wordScan.next();
for(int numLetters = word.length() - 1; numLetters >= 0; numLetters--)
tempWord += word.charAt(numLetters);
System.out.print(tempWord + " ");
tempWord = "";
}
System.out.println();
}
}
this bit adds in the spaces
System.out.print(tempWord + " ");
this bit reverses it
for(int numLetters = word.length() - 1; numLetters >= 0; numLetters--)
tempWord += word.charAt(numLetters);
this bit sets it up for the next word
tempWord = "";
The for loop counts backwards, from the index of the last character in the word to the first (in zero based notation)
The print prints the reversed word + a space (" "), the fact it uses print in place of println is because println would add a carriage return putting each word in a different line.
The tempWord = ""; at the end of each iteration reset the variable so it can be reused.