Develop Reference

Java: Print a unique character in a string

I'm writing a program that will print the unique character in a string (entered through a scanner). I've created a method that tries to accomplish this but I keep getting characters that are not repeats, instead of a character (or characters) that is unique to the string. I want the unique letters only.
Here's my code:
import java.util.Scanner;
public class Sameness{
public static void main (String[]args){
Scanner kb = new Scanner (System.in);
String word = "";
System.out.println("Enter a word: ");
word = kb.nextLine();
uniqueCharacters(word);
}
public static void uniqueCharacters(String test){
String temp = "";
for (int i = 0; i < test.length(); i++){
if (temp.indexOf(test.charAt(i)) == - 1){
temp = temp + test.charAt(i);
}
}
System.out.println(temp + " ");
}
}
And here's sample output with the above code:
Enter a word:
nreena
nrea
The expected output would be: ra

Based on your desired output, you have to replace a character that initially has been already added when it has a duplicated later, so:
public static void uniqueCharacters(String test){
String temp = "";
for (int i = 0; i < test.length(); i++){
char current = test.charAt(i);
if (temp.indexOf(current) < 0){
temp = temp + current;
} else {
temp = temp.replace(String.valueOf(current), "");
}
}
System.out.println(temp + " ");
}

How about applying the KISS principle:
public static void uniqueCharacters(String test) {
System.out.println(test.chars().distinct().mapToObj(c -> String.valueOf((char)c)).collect(Collectors.joining()));
}

The accepted answer will not pass all the test case for example
input -"aaabcdd"
desired output-"bc"
but the accepted answer will give -abc
because the character a present odd number of times.
Here I have used ConcurrentHasMap to store character and the number of occurrences of character then removed the character if the occurrences is more than one time.
import java.util.concurrent.ConcurrentHashMap;
public class RemoveConductive {
public static void main(String[] args) {
String s="aabcddkkbghff";
String[] cvrtar=s.trim().split("");
ConcurrentHashMap<String,Integer> hm=new ConcurrentHashMap<>();
for(int i=0;i<cvrtar.length;i++){
if(!hm.containsKey(cvrtar[i])){
hm.put(cvrtar[i],1);
}
else{
hm.put(cvrtar[i],hm.get(cvrtar[i])+1);
}
}
for(String ele:hm.keySet()){
if(hm.get(ele)>1){
hm.remove(ele);
}
}
for(String key:hm.keySet()){
System.out.print(key);
}
}
}

Though to approach a solution I would suggest you to try and use a better data structure and not just string. Yet, you can simply modify your logic to delete already existing duplicates using an else as follows :
public static void uniqueCharacters(String test) {
String temp = "";
for (int i = 0; i < test.length(); i++) {
char ch = test.charAt(i);
if (temp.indexOf(ch) == -1) {
temp = temp + ch;
} else {
temp.replace(String.valueOf(ch),""); // added this to your existing code
}
}
System.out.println(temp + " ");
}

This is an interview question. Find Out all the unique characters of a string.
Here is the complete solution. The code itself is self explanatory.
public class Test12 {
public static void main(String[] args) {
String a = "ProtijayiGiniGina";
allunique(a);
}
private static void allunique(String a) {
int[] count = new int[256];// taking count of characters
for (int i = 0; i < a.length(); i++) {
char ch = a.charAt(i);
count[ch]++;
}
for (int i = 0; i < a.length(); i++) {
char chh = a.charAt(i);
// character which has arrived only one time in the string will be printed out
if (count[chh] == 1) {
System.out.println("index => " + i + " and unique character => " + a.charAt(i));
}
}
}// unique
}
In Python :
def firstUniqChar(a):
count = [0] *256
for i in a: count[ord(i)] += 1
element = ""
for item in a:
if (count[ord(item)] == 1):
element = item;
break;
return element
a = "GiniGinaProtijayi";
print(firstUniqChar(a)) # output is P

public static String input = "10 5 5 10 6 6 2 3 1 3 4 5 3";
public static void uniqueValue (String numbers) {
String [] str = input.split(" ");
Set <String> unique = new HashSet <String> (Arrays.asList(str));
System.out.println(unique);
for (String value:unique) {
int count = 0;
for ( int i= 0; i<str.length; i++) {
if (value.equals(str[i])) {
count++;
}
}
System.out.println(value+"\t"+count);
}
}
public static void main(String [] args) {
uniqueValue(input);
}

Step1: To find the unique characters in a string, I have first taken the string from user.
Step2: Converted the input string to charArray using built in function in java.
Step3: Considered two HashSet (set1 for storing all characters even if it is getting repeated, set2 for storing only unique characters.
Step4 : Run for loop over the array and check that if particular character is not there in set1 then add it to both set1 and set2. if that particular character is already there in set1 then add it to set1 again but remove it from set2.( This else part is useful when particular character is getting repeated odd number of times).
Step5 : Now set2 will have only unique characters. Hence, just print that set2.
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
String str = input.next();
char arr[] = str.toCharArray();
HashSet<Character> set1=new HashSet<Character>();
HashSet<Character> set2=new HashSet<Character>();
for(char i:arr)
{
if(set1.contains(i))
{
set1.add(i);
set2.remove(i);
}
else
{
set1.add(i);
set2.add(i);
}
}
System.out.println(set2);
}

I would store all the characters of the string in an array that you will loop through to check if the current characters appears there more than once. If it doesn't, then add it to temp.
public static void uniqueCharacters(String test) {
String temp = "";
char[] array = test.toCharArray();
int count; //keep track of how many times the character exists in the string
outerloop: for (int i = 0; i < test.length(); i++) {
count = 0; //reset the count for every new letter
for(int j = 0; j < array.length; j++) {
if(test.charAt(i) == array[j])
count++;
if(count == 2){
count = 0;
continue outerloop; //move on to the next letter in the string; this will skip the next two lines below
}
}
temp += test.charAt(i);
System.out.println("Adding.");
}
System.out.println(temp);
}
I have added comments for some more detail.

import java.util.*;
import java.lang.*;
class Demo
{
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter String");
String s1=sc.nextLine();
try{
HashSet<Object> h=new HashSet<Object>();
for(int i=0;i<s1.length();i++)
{
h.add(s1.charAt(i));
}
Iterator<Object> itr=h.iterator();
while(itr.hasNext()){
System.out.println(itr.next());
}
}
catch(Exception e)
{
System.out.println("error");
}
}
}

If you don't want to use additional space:
String abc="developer";
System.out.println("The unique characters are-");
for(int i=0;i<abc.length();i++)
{
for(int j=i+1;j<abc.length();j++)
{
if(abc.charAt(i)==abc.charAt(j))
abc=abc.replace(String.valueOf(abc.charAt(j))," ");
}
}
System.out.println(abc);
Time complexity O(n^2) and no space.

This String algorithm is used to print unique characters in a string.It runs in O(n) runtime where n is the length of the string.It supports ASCII characters only.
static String printUniqChar(String s) {
StringBuilder buildUniq = new StringBuilder();
boolean[] uniqCheck = new boolean[128];
for (int i = 0; i < s.length(); i++) {
if (!uniqCheck[s.charAt(i)]) {
uniqCheck[s.charAt(i)] = true;
if (uniqCheck[s.charAt(i)])
buildUniq.append(s.charAt(i));
}
}

public class UniqueCharactersInString {
public static void main(String []args){
String input = "aabbcc";
String output = uniqueString(input);
System.out.println(output);
}
public static String uniqueString(String s){
HashSet<Character> uniques = new HashSet<>();
uniques.add(s.charAt(0));
String out = "";
out += s.charAt(0);
for(int i =1; i < s.length(); i++){
if(!uniques.contains(s.charAt(i))){
uniques.add(s.charAt(i));
out += s.charAt(i);
}
}
return out;
}
}
What would be the inneficiencies of this answer? How does it compare to other answers?

Based on your desired output you can replace each character already present with a blank character.
public static void uniqueCharacters(String test){
String temp = "";
for(int i = 0; i < test.length(); i++){
if (temp.indexOf(test.charAt(i)) == - 1){
temp = temp + test.charAt(i);
} else {
temp.replace(String.valueOf(temp.charAt(i)), "");
}
}
System.out.println(temp + " ");
}

public void uniq(String inputString) {
String result = "";
int inputStringLen = inputStr.length();
int[] repeatedCharacters = new int[inputStringLen];
char inputTmpChar;
char tmpChar;
for (int i = 0; i < inputStringLen; i++) {
inputTmpChar = inputStr.charAt(i);
for (int j = 0; j < inputStringLen; j++) {
tmpChar = inputStr.charAt(j);
if (inputTmpChar == tmpChar)
repeatedCharacters[i]++;
}
}
for (int k = 0; k < inputStringLen; k++) {
inputTmpChar = inputStr.charAt(k);
if (repeatedCharacters[k] == 1)
result = result + inputTmpChar + " ";
}
System.out.println ("Unique characters: " + result);
}
In first for loop I count the number of times the character repeats in the string. In the second line I am looking for characters repetitive once.

how about this :)
for (int i=0; i< input.length();i++)
if(input.indexOf(input.charAt(i)) == input.lastIndexOf(input.charAt(i)))
System.out.println(input.charAt(i) + " is unique");

package extra;
public class TempClass {
public static void main(String[] args) {
// TODO Auto-generated method stub
String abcString="hsfj'pwue2hsu38bf74sa';fwe'rwe34hrfafnosdfoasq7433qweid";
char[] myCharArray=abcString.toCharArray();
TempClass mClass=new TempClass();
mClass.countUnique(myCharArray);
mClass.countEach(myCharArray);
}
/**
* This is the program to find unique characters in array.
* #add This is nice.
* */
public void countUnique(char[] myCharArray) {
int arrayLength=myCharArray.length;
System.out.println("Array Length is: "+arrayLength);
char[] uniqueValues=new char[myCharArray.length];
int uniqueValueIndex=0;
int count=0;
for(int i=0;i<arrayLength;i++) {
for(int j=0;j<arrayLength;j++) {
if (myCharArray[i]==myCharArray[j] && i!=j) {
count=count+1;
}
}
if (count==0) {
uniqueValues[uniqueValueIndex]=myCharArray[i];
uniqueValueIndex=uniqueValueIndex+1;
count=0;
}
count=0;
}
for(char a:uniqueValues) {
System.out.println(a);
}
}
/**
* This is the program to find count each characters in array.
* #add This is nice.
* */
public void countEach(char[] myCharArray) {
}
}

Here str will be your string to find the unique characters.
function getUniqueChars(str){
let uniqueChars = '';
for(let i = 0; i< str.length; i++){
for(let j= 0; j< str.length; j++) {
if(str.indexOf(str[i]) === str.lastIndexOf(str[j])) {
uniqueChars += str[i];
}
}
}
return uniqueChars;
}

public static void main(String[] args) {
String s = "aaabcdd";
char a[] = s.toCharArray();
List duplicates = new ArrayList();
List uniqueElements = new ArrayList();
for (int i = 0; i < a.length; i++) {
uniqueElements.add(a[i]);
for (int j = i + 1; j < a.length; j++) {
if (a[i] == a[j]) {
duplicates.add(a[i]);
break;
}
}
}
uniqueElements.removeAll(duplicates);
System.out.println(uniqueElements);
System.out.println("First Unique : "+uniqueElements.get(0));
}
Output :
[b, c]
First Unique : b

import java.util.*;
public class Sameness{
public static void main (String[]args){
Scanner kb = new Scanner (System.in);
String word = "";
System.out.println("Enter a word: ");
word = kb.nextLine();
uniqueCharacters(word);
}
public static void uniqueCharacters(String test){
for(int i=0;i<test.length();i++){
if(test.lastIndexOf(test.charAt(i))!=i)
test=test.replaceAll(String.valueOf(test.charAt(i)),"");
}
System.out.println(test);
}
}

public class Program02
{
public static void main(String[] args)
{
String inputString = "abhilasha";
for (int i = 0; i < inputString.length(); i++)
{
for (int j = i + 1; j < inputString.length(); j++)
{
if(inputString.toCharArray()[i] == inputString.toCharArray()[j])
{
inputString = inputString.replace(String.valueOf(inputString.charAt(j)), "");
}
}
}
System.out.println(inputString);
}
}

Shortest and Longest word in a sentence in Java

I am new in Java Programming! So tried to solve a problem to find the shortest and longest word in a sentence. My program is shown below . I hope you people can show me the right direction about my program -
public class StringProblems {
void shortAndLongWord(String str) {
String sw = "", lw = "";
int s = str.length(), l = 0;
String words[] = str.split(" ");
for(String word:words) {
if(word.length()<s)
sw = word;
else if(word.length()>l)
lw = word;
}
System.out.println("LONGEST WORD : "+lw);
System.out.println("SHORTEST WORD : "+sw);
}
public static void main(String[] args) {
Scanner scr = new Scanner(System.in);
StringProblems obj = new StringProblems();
System.out.printf("Enter a line to get shortest and longest word:");
String str = scr.nextLine();
str += " ";
obj.shortAndLongWord(str);
}
}
Output of this program is :
*Enter a line to get shortest and logest word:This is Sentence
LONGEST WORD :
SHORTEST WORD : Sentence**
I dont know where my logic went wrong! Please help me to solve!

You have to keep updating the length of the current shortest and longest word:
public class StringProblems {
void shortAndLongWord(String str)
{
if (str == null)
return;
String sw="",lw="";
int s=str.length(),l=0;
String words[]=str.split(" ");
for(String word:words)
{
if(word.length()<s)
{
sw=word;
s = word.length();
}
if(word.length()>l)
{
lw=word;
l = word.length();
}
}
System.out.println("LONGEST WORD : "+lw);
System.out.println("SHORTEST WORD : "+sw);
}
public static void main(String[] args) {
Scanner scr=new Scanner(System.in);
StringProblems obj=new StringProblems();
System.out.printf("Enter a line to get shortest and longest word:");
String str=scr.nextLine();
str+=" ";
obj.shortAndLongWord(str);
}
}

You need to keep updating l (length of the longest word) and s (length of the smallest word)
if(word.length()<s)
{
sw=word;
s = word.length();
}
if(word.length()>l)
{
lw=word;
l = word.length();
}
Also, there are boundary conditions that you need to take care of.
For example, what happens if the string is a single word. What happens when the input string is null etc.

import java.util.Scanner;
public class ShortestAndLongestWordInALine {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter any sentence : ");
String line = sc.nextLine();
sc.close();
int shortestWordLength = 0;
int longestWordLength = 0;
String shortestWord = "";
String longestWord = "";
int tempLength = 0;
String[] eachWordArray = line.split(" ");
boolean firstTime = false;
for (String eachWord : eachWordArray) {
tempLength = eachWord.length();
if (firstTime == false) {
firstTime = true;
shortestWordLength = tempLength;
shortestWord = eachWord;
longestWordLength = tempLength;
longestWord = eachWord;
}
if (tempLength > 0) {
if (tempLength < shortestWordLength) {
shortestWordLength = tempLength;
shortestWord = eachWord;
} else if (tempLength > longestWordLength) {
longestWordLength = tempLength;
longestWord = eachWord;
}
}
}
System.out.println("shortestWordLength = " + shortestWordLength + " shortestWord = " + shortestWord);
System.out.println("longestWordLength = " + longestWordLength + " longestWord = " + longestWord);
}
}

You are not updating values of l and s during iteration. You should try something like this:
if (word.length() < s) {
sw = word;
s = word.length();
} else if (word.length() > l) {
lw = word;
l = word.length();
}

import java.util.*;
class lw
{
public static void main()
{
Scanner in=new Scanner(System.in);
String z=" ",lw="";
int q=0,o=0;
System.out.println("Enter string");
String str=in.nextLine()+" ";
int l=str.length();
for(int i=1;i<l;i++)
{
char ch=str.charAt(i);
if(ch!=' ')
z=z+ch;
else
{
q=z.length();
if(q>o)
lw=z;
o=q;
z="";
}
}
System.out.println("lw= "+lw);
System.out.println("length="+q);
}
}

For loop isn't printing correct "."

What I am trying to do is have it take a java file that look like this
public class test1 {
public static void main ( string[] args ) {
System.out.println( "This is Test 1." );
}
}
And it is suppose to output a text file with the proper spacing and indents.
So far I can get the correct indenting for the first the lines. But I am having trouble with my second for loop that prints the spaces for the ending brackets. The ending brackets are prints outward like the first 3 lines instead of inward. Sorry if my variables are confusing.
Here is my code so far
public class JavaJustifier {
public static void main( String[] args )
throws FileNotFoundException {
for( int i = 1; i < 6; i++ ) {
justifyJava( "Test" + i + ".java",
"Justified" + i + ".txt",
4 );
}
}
public static void justifyJava( String inputFileName,
String outputFileName,
int tabSize )
throws FileNotFoundException {
int counter = 0;
int counter2 = 0;
int blah = 0;
File f = new File(inputFileName);
File p = new File(outputFileName);
if (p.exists())
p.delete();
Scanner input = new Scanner (f);
PrintStream name = new PrintStream(new File(outputFileName));
while (input.hasNextLine()) {
String line = input.nextLine();
Scanner lineScan = new Scanner(line);
if (line.contains("{") == true) {
name.print("{\r\n");
counter++;
for (int i = 1; i <= counter; i++) {
for (int j = 0; j <= tabSize; j++) {
name.print(" ");
}
}
System.out.println(counter);
} else if (line.contains("}") == true) {
name.print("\r\n");
counter--;
for (int x = 1; x <= counter; x++) {
for (int y = 1; y <= tabSize; y++) {
name.print(" ");
}
}
name.print("}");
System.out.println(counter);
} else {
name.print(line);
}
}
}
What it gives me is
public class Test1
{
public static void main( String[] args )
{
System.out.println( "This is Test 1." );
}
}
What I desire is this
public class Test1
{
public static void main( String[] args )
{
System.out.println( "This is Test 1." );
}
}

Okay, I've refactored a few things (and it was necessary) but it works exactly as you expect it to (AFAIK!).
Here's the code:
public class JavaJustifier {
static int counter = 0;
static int tabSize = 4;
public static void main(String[] args) throws FileNotFoundException {
justifyJava("Test1.java", "Justified1.txt");
}
private static void processLine(PrintStream name, String line) {
if (line.contains("{")) {
String preText = line.substring(0, line.indexOf("{"));
String postText = line.substring(line.indexOf("{") + 1)
.replaceAll("\\n", "").replaceAll("\\r\\n", "");
printSpaces(name);
name.println(preText);
printSpaces(name);
name.println("{");
counter++;
processLine(name, postText);
} else if (line.contains("}")) {
String preText = line.substring(0, line.indexOf("}"));
String postText = line.substring(line.indexOf("}") + 1)
.replaceAll("\\n", "").replaceAll("\\r\\n", "");
name.println(preText);
counter--;
printSpaces(name);
name.println("}");
processLine(name, postText);
} else {
if (!line.equals("\r\n") && line.length() != 0) {
printSpaces(name);
name.print(line);
}
}
}
private static void printSpaces(PrintStream p) {
for (int i = 1; i <= counter; i++) {
for (int j = 0; j <= tabSize; j++) {
p.print(" ");
}
}
}
public static void justifyJava(String inputFileName, String outputFileName)
throws FileNotFoundException {
File f = new File(inputFileName);
File p = new File(outputFileName);
if (p.exists())
p.delete();
Scanner input = new Scanner(f);
PrintStream name = new PrintStream(new File(outputFileName));
while (input.hasNextLine()) {
String line = input.nextLine().trim();
processLine(name, line);
}
}
}

Java Array Index Out of Bounds Exception [duplicate]

This question already has an answer here:
Closed 10 years ago.
I run through the entire code. I am able to enter a simple .txt file to search for a word. After it asks for a word, it returns
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -48
at SearchEngine.main(SearchEngine.java:150)
Line 150 is for (int j = 0; j
Any help debugging?
This is basic search engine program that should be able to search a .txt file for any word.
Assignment link: http://cis-linux1.temple.edu/~yates/cis1068/sp12/homeworks/concordance/concordance.html
import java.util.*;
import java.io.*;
public class SearchEngine {
public static int getNumberOfWords (File f) throws FileNotFoundException {
int numWords = 0;
Scanner scan = new Scanner(f);
while (scan.hasNext()) {
numWords++;
scan.next();
}
scan.close();
return numWords;
}
public static void readInWords (File input, String [] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int i = 0;
while (scan.hasNext() && i<x.length) {
x[i] = scan.next();
i++;
}
scan.close();
}
public static int getNumOfDistinctWords (File input, String [] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int count = 0;
int i = 1;
while (scan.hasNext() && i<x.length) {
if (!x[i].equals(x[i-1])) {
count++;
}
i++;
}
scan.close();
return count;
}
public static void readInDistinctWords (String [] x, String [] y) {
int i = 1;
int k = 0;
while (i<x.length) {
if (!x[i].equals(x[i-1])) {
y[k] = x[i];
k++;
}
i++;
}
}
public static int getNumberOfLines (File input) throws FileNotFoundException {
int numLines = 0;
Scanner scan = new Scanner(input);
while (scan.hasNextLine()) {
numLines++;
scan.nextLine();
}
scan.close();
return numLines;
}
public static void readInLines (File input, String [] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int i = 0;
while (scan.hasNextLine() && i<x.length) {
x[i] = scan.nextLine();
i++;
}
scan.close();
}
public static void main(String [] args) {
try {
//gets file name
System.out.println("Enter the name of the text file you wish to search");
Scanner kb = new Scanner(System.in);
String fileName = kb.nextLine();
String TXT = ".txt";
if (!fileName.endsWith(TXT)) {
fileName = fileName.concat(TXT);
}
File input = new File(fileName);
//First part of creating index
System.out.println("Creating vocabArray");
int NUM_WORDS = getNumberOfWords(input);
//System.out.println(NUM_WORDS);
String [] wordArray = new String[NUM_WORDS];
readInWords(input, wordArray);
Arrays.sort(wordArray);
int NUM_DISTINCT_WORDS = getNumOfDistinctWords(input, wordArray);
String [] vocabArray = new String[NUM_DISTINCT_WORDS];
readInDistinctWords(wordArray, vocabArray);
System.out.println("Finished creating vocabArray");
System.out.println("Creating concordanceArray");
int NUM_LINES = getNumberOfLines(input);
String [] concordanceArray = new String[NUM_LINES];
readInLines(input, concordanceArray);
System.out.println("Finished creating concordanceArray");
System.out.println("Creating invertedIndex");
int [][] invertedIndex = new int[NUM_DISTINCT_WORDS][10];
int [] wordCountArray = new int[NUM_DISTINCT_WORDS];
int lineNum = 0;
while (lineNum<concordanceArray.length) {
Scanner scan = new Scanner(concordanceArray[lineNum]);
while (scan.hasNext()) {
int wordPos = Arrays.binarySearch(vocabArray, scan.next());
wordCountArray[wordPos]+=1;
for(int i = 0; i < invertedIndex.length; i++) {
for(int j = 0; j < invertedIndex[i].length; j++) {
if (invertedIndex[i][j] == 0) {
invertedIndex[i][j] = lineNum;
break;
} } }
}
lineNum++;
}
System.out.println("Finished creating invertedIndex");
}
System.out.println("Enter a word to be searched (type quit to exit program)");
Scanner keyboard = new Scanner(System.in);
String searchWord = keyboard.next();
while (!searchWord.equals("quit")) {
int counter = 0;
int wordPos = Arrays.binarySearch(allWordsArray, searchWord);
for (int j = 0; j<invertedIndex[wordPos].length; j++) {
if(invertedIndex[wordPos][j] != 0) {
int number = invertedIndex[wordPos][j];
String printOut = concordanceArray[number];
System.out.print(number);
System.out.print(" :");
System.out.println(printOut);
}
}
}
catch (FileNotFoundException exception) {
System.out.println("File Not Found");
}
} //main
} //class

From what I can see your getNumOfDistinctWords(String[] x) is wrong. This is returning a value of one less than it should be. Here is a modified version of the code:
import java.util.*;
import java.io.*;
public class SearchEngine {
//Counts the number of words in the file
public static int getNumberOfWords (File f) throws FileNotFoundException {
int numWords = 0;
Scanner scan = new Scanner(f);
while (scan.hasNext()) {
numWords++;
scan.next();
}
scan.close();
return numWords;
}
public static void readInWords (File input, String[] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int i = 0;
while (scan.hasNext() && i < x.length) {
x[i] = scan.next();
i++;
}
scan.close();
}
public static String[] getNumOfDistinctWords (String[] x) throws FileNotFoundException {
HashSet<String> distinctWords = new HashSet<String>();
for(int i=0; i<x.length; i++){
distinctWords.add(x[i]);
}
String[] distinctWordsArray = new String[distinctWords.size()];
int i = 0;
for(String word : distinctWords){
distinctWordsArray[i] = word;
i++;
}
return distinctWordsArray;
}
public static int getNumberOfLines (File input) throws FileNotFoundException {
int numLines = 0;
Scanner scan = new Scanner(input);
while (scan.hasNextLine()) {
numLines++;
scan.nextLine();
}
scan.close();
return numLines;
}
public static void readInLines (File input, String [] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int i = 0;
while (scan.hasNextLine() && i<x.length) {
x[i] = scan.nextLine();
i++;
}
scan.close();
}
public static void main(String [] args) {
try {
//gets file name
System.out.println("Enter the name of the text file you wish to search");
Scanner kb = new Scanner(System.in);
String fileName = kb.nextLine();
String TXT = ".txt";
if (!fileName.endsWith(TXT)) {
fileName = fileName.concat(TXT);
}
File input = new File(fileName);
//First part of creating index
System.out.println("Creating vocabArray");
int NUM_WORDS = getNumberOfWords(input);
//Output the number of words in the file
System.out.println("Number of words is: " + NUM_WORDS);
String[] allWordsArray = new String[NUM_WORDS];
readInWords(input, allWordsArray);
Arrays.sort(allWordsArray);
String[] distinctWordsArray = getNumOfDistinctWords(allWordsArray);
//Output the number of distinct words
System.out.println("Number of distinct words is: " + distinctWordsArray.length);
System.out.println("Finished creating distinctWordsArray");
System.out.println("Creating concordanceArray");
int NUM_LINES = getNumberOfLines(input);
String[] concordanceArray = new String[NUM_LINES];
readInLines(input, concordanceArray);
System.out.println("Finished creating concordanceArray");
System.out.println("Creating invertedIndex");
int [][] invertedIndex = new int[distinctWordsArray.length][10];
int [] wordCountArray = new int[distinctWordsArray.length];
int lineNum = 0;
while (lineNum < concordanceArray.length) {
Scanner scan = new Scanner(concordanceArray[lineNum]);
while (scan.hasNext()) {
//Find the position the word appears on the line, if word not found returns a number less than 0
int wordPos = Arrays.binarySearch(distinctWordsArray, scan.next());
if(wordPos > -1){
wordCountArray[wordPos] += 1;
}
for(int i = 0; i < invertedIndex.length; i++) {
for(int j = 0; j < invertedIndex[i].length; j++) {
if (invertedIndex[i][j] == 0) {
invertedIndex[i][j] = lineNum;
break;
} } }
}
lineNum++;
}
System.out.println("Finished creating invertedIndex");
}
catch (FileNotFoundException exception) {
System.out.println("File Not Found");
}
} //main
} //class
I should also point out the fact that Arrays.binarySearch(distinctWordsArray, scan.next()); will return a number less than 0 if the word is not found on that line. This is why you are getting the Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 as wordCountArray is being referenced at index -1 which of course doesn't exist!
The code after this also looks buggy but I'll let you fix that!!

Without knowing exactly where line 126 is, finding this specific bug is just too much hassle. But I've got some advice for the rest of the code:
int NUM_DISTINCT_WORDS = getNumOfDistinctWords(input, wordArray);
Normally, variables in all-caps are constants that are assigned at compile time. It's a tradition that comes from C days, when it was wonderful to know which "variables" were actually replaced by the preprocessor. But the convention has proven to be useful in other languages, and most programmers would expect NUM_DISTINCT_WORDS to be assigned a specific value at compile time.
This code is simply unreadable:
for(int i = 0; i < invertedIndex.length; i++) {
for(int j = 0; j < invertedIndex[i].length; j++) {
if (invertedIndex[i][j] == 0) {
invertedIndex[i][j] = lineNum;
break;
} } }
A more idiomatic way to show these nested loops is:
for (int i = 0; i < invertedIndex.length; i++) {
for (int j = 0; j < invertedIndex[i].length; j++) {
if (invertedIndex[i][j] == 0) {
invertedIndex[i][j] = lineNum;
break;
}
}
}
Because I use the standard Lindent script to do re-indenting, I get tabs. You don't have to use tabs, but they are convenient to add and delete with a single keystroke, and they are deep enough to be obviously visible even with smallish type faces. You'll find your code far easier to work with if you follow the standard indenting idioms.
The following piece of code is extremely unfortunate:
catch(FileNotFoundException exception) {
System.out.println("File Not Found");
}
It would be better to catch a higher-level exception and include the exception message. You can more easily handle dozens of errors if you catch an exception higher in the hierarchy, and the error messages will be far more informative.
Your main() method performs a lot of detailed work. I think your code would be easier to test, easier to debug, and easier to read, if you break it apart into more methods. Try to get the main() to read practically like a high-level description of your code.
With the line with the bug on it now easily visible, I can spot the problem:
int wordPos = Arrays.binarySearch(vocabArray, scan.next());
wordCountArray[wordPos]+=1;
You've looked up the wordPos in the vocabArray, but modified content in the wordCountArray. Are you sure they are the same size and have the same meanings?

Java Search Engine Debugging [closed]

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Closed 10 years ago.
I run through the entire code. I am able to enter a simple .txt file to search for a word. After it asks for a word, it returns
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -48 at SearchEngine.main(SearchEngine.java:150)
Line 150 is for (int j = 0; j
Any help debugging?
This is basic search engine program that should be able to search a .txt file for any word.
Assignment link: http://cis-linux1.temple.edu/~yates/cis1068/sp12/homeworks/concordance/concordance.html
import java.util.*;
import java.io.*;
public class SearchEngine {
//Counts the number of words in the file
public static int getNumberOfWords (File f) throws FileNotFoundException {
int numWords = 0;
Scanner scan = new Scanner(f);
while (scan.hasNext()) {
numWords++;
scan.next();
}
scan.close();
return numWords;
}
public static void readInWords (File input, String[] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int i = 0;
while (scan.hasNext() && i < x.length) {
x[i] = scan.next();
i++;
}
scan.close();
}
public static String[] getNumOfDistinctWords (String[] x) throws FileNotFoundException {
HashSet<String> distinctWords = new HashSet<String>();
for(int i=0; i<x.length; i++){
distinctWords.add(x[i]);
}
String[] distinctWordsArray = new String[distinctWords.size()];
int i = 0;
for(String word : distinctWords){
distinctWordsArray[i] = word;
i++;
}
return distinctWordsArray;
}
public static int getNumberOfLines (File input) throws FileNotFoundException {
int numLines = 0;
Scanner scan = new Scanner(input);
while (scan.hasNextLine()) {
numLines++;
scan.nextLine();
}
scan.close();
return numLines;
}
public static void readInLines (File input, String [] x) throws FileNotFoundException {
Scanner scan = new Scanner(input);
int i = 0;
while (scan.hasNextLine() && i<x.length) {
x[i] = scan.nextLine();
i++;
}
scan.close();
}
public static void main(String [] args) {
try {
//gets file name
System.out.println("Enter the name of the text file you wish to search");
Scanner kb = new Scanner(System.in);
String fileName = kb.nextLine();
String TXT = ".txt";
if (!fileName.endsWith(TXT)) {
fileName = fileName.concat(TXT);
}
File input = new File(fileName);
//First part of creating index
System.out.println("Creating vocabArray");
int NUM_WORDS = getNumberOfWords(input);
//Output the number of words in the file
System.out.println("Number of words is: " + NUM_WORDS);
String[] allWordsArray = new String[NUM_WORDS];
readInWords(input, allWordsArray);
Arrays.sort(allWordsArray);
String[] distinctWordsArray = getNumOfDistinctWords(allWordsArray);
//Output the number of distinct words
System.out.println("Number of distinct words is: " + distinctWordsArray.length);
System.out.println("Finished creating distinctWordsArray");
System.out.println("Creating concordanceArray");
int NUM_LINES = getNumberOfLines(input);
String[] concordanceArray = new String[NUM_LINES];
readInLines(input, concordanceArray);
System.out.println("Finished creating concordanceArray");
System.out.println("Creating invertedIndex");
int [][] invertedIndex = new int[distinctWordsArray.length][10];
int [] wordCountArray = new int[distinctWordsArray.length];
int lineNum = 0;
while (lineNum < concordanceArray.length) {
Scanner scan = new Scanner(concordanceArray[lineNum]);
while (scan.hasNext()) {
//Find the position the word appears on the line, if word not found returns a number less than 0
int wordPos = Arrays.binarySearch(distinctWordsArray, scan.next());
if(wordPos > -1){
wordCountArray[wordPos] += 1;
}
for(int i = 0; i < invertedIndex.length; i++) {
for(int j = 0; j < invertedIndex[i].length; j++) {
if (invertedIndex[i][j] == 0) {
invertedIndex[i][j] = lineNum;
break;
}
}
}
}
lineNum++;
}
System.out.println("Finished creating invertedIndex");
System.out.println("Enter a word to be searched (type quit to exit program)");
Scanner keyboard = new Scanner(System.in);
String searchWord = keyboard.next();
while (!searchWord.equals("quit")) {
int counter = 0;
int wordPos = Arrays.binarySearch(allWordsArray, searchWord);
for (int j = 0; j<invertedIndex[wordPos].length; j++) {
if(invertedIndex[wordPos][j] != 0) {
int number = invertedIndex[wordPos][j];
String printOut = concordanceArray[number];
System.out.print(number);
System.out.print(" :");
System.out.println(printOut);
}
}
}
}
catch (FileNotFoundException exception) {
System.out.println("File Not Found");
}
} //main
} //class

int wordPos = Arrays.binarySearch(allWordsArray, searchWord);
wordPos will be negative when the searchWord is not in the array. Therefore,
in for (int j = 0; j<invertedIndex[wordPos].length; j++) {, invertedIndex[wordPos] will be trying to access a negative index of the array, in your case, -48
You should do something like this before the loop:
if(wordPos < 0){
// Do something
}else {
for (int j = 0; j<invertedIndex[wordPos].length; j++) {
...
}
You should read the Javadoc, specially the doc for returns. You will get your answer about -48.