this is my first post so forgive me if i have posted incorrectly. I have a task that i need to complete but i cant get it to work properly. the compiler that i use is bluej. what i need to do is to use scanner to read a text file and compare a user input to the text file. if the input string compares then it should print out that ""The word is on the text file". Unfortunately i cant get this to work. My code reads the file because it prints out to the console but no comparison it s happening. please have a look at my code and give me some pointers. i have been trying to use .equals():
private boolean searchFromRecord(String recordName, String word) throws IOException
{
// Please write your code after this line
File file = new File(recordName);
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
for(int i = 0; scanner.hasNextLine(); i++){
String compare = scanner.nextLine();
IO.outputln("word#" + i + ":" + compare);
}
scanner.close();
if (scanner.equals(word)){
return true;
} else{
return false;
}
}
return true;
}
this is what i get output in the console:
Input a word: IRON
AA 888
word#0:BULLET
word#1:1
word#2:AE 1688
word#3:CHEERS
word#4:GAMES
word#5:IRON MAN
word#6:WOLF
word#7:Testing
word#8:Wonderful
The word "IRON" is not in the record.
Here are some problems, along with why they are problems & a suggestion on how they could be fixed:
Problem: closing a scanner within the a loop that uses it will cause an exception. Reason: after we go through the loop once, the scanner will be closed. when we loop through again, an error will occur since the loop uses the scanner, which means the scanner should be "open". Possible solution: move scanner.close() to after the while loop.
Problem: we shouldn't return true at the end of this method. Reason: I'm guessing that this method is supposed to return true if the word is found, and false otherwise. Now, the only way to get to this return statement is if our word doesn't exist in the recordFile; it should return false. Possible solution: return false at the end of the method instead.
Problem: the first line in recordFile will never be checked for equality with word Reason: each method call of scanner.nextLine() will return each line from the recordFile as a String once and only once. In your code, it is called once in the beginning of the while loop's body, but not used to compare with word, then after, it is used in the for loop for comparison Possible solution: remove the line: System.out.println(scanner.nextLine());.
Problem: scanner.equals(word) will probably always return false. Reason: scanner is a Scanner, and word is a String, they should never be equal. Possible solution: replace scanner.equals(word) with compare.equals(word)
Problem: word is not actually compared with each compare. Reason: it is outside the for loop. Possible solution: move the if else block into the end of the for loop's body.
I don't think the while loop is really needed. I strongly recommend that the while loop, is removed, but keep the body.
Problem: Moving the if else block into the for loop, and above the scanner.close() means that the scanner.close() will never be run. Reason: once a return statement is executed, the flow of control immediatly exits the method, and returns to where the method was invoked which makes code after return statements useless. Possible solution: instead of returning right away, declare some sort of boolean variable that will store the return value. have the return value be modified throughout the method, then return the variable at the very end, after scaner.close()
There are many many other ways to fix each of these problems other than the ones suggested here.
I hope you find this helpful! :)
your code, refactored to implement the suggested solutions above:
private boolean searchFromRecord(String recordName, String word) throws IOException {
// Please write your code after this line
Boolean wordFound = false; // indicates if word exists in recordFile.
File file = new File(recordName); // file at path "recordName"
Scanner scanner = new Scanner(file); // reads records from "file"
// iterate through the recordFile, to see if "word" already exists
// within recordFile.
for(int i = 0; scanner.hasNextLine(); i++) {
// read the record from the file
String compare = scanner.nextLine();
IO.outputln("word#" + i + ":" + compare);
// compare the record with our word
if (compare.equals(word)){
wordFound = true;
break; // bail out of loop, our work here is done
}
}
// clean up, and return...
scanner.close();
return wordFound;
}
First, scanner is not a String and it will not equal a String. Second, you are dropping lines - scanner.nextLine() gets the next line, and you print it (but don't save it or compare it). I think you wanted something more like this,
// eats and tosses input.
// System.out.println(scanner.nextLine());
String line = scanner.nextLine();
for(int i = 0; scanner.hasNextLine(); i++){
String compare = scanner.nextLine();
IO.outputln("word#" + i + ": " + compare + " to line: " + line);
if (line.contains(compare)){ // "IRON MAN" starts with "IRON", it doesn't equal IRON.
return true;
}
}
scanner.close();
return false; // <-- default.
Another flavor is to read the whole file into a String variable and look for specified String inside the String.
Code:
File file = new File("C:\\Users\\KICK\\Documents\\NetBeansProjects"
+ "\\SearchWordinFile\\src\\searchwordinfile\\words.txt");
String s="";
try(Scanner input = new Scanner(file)){
input.useDelimiter("\\A");
if (input.hasNext()) {
s = input.next();
}
}catch(Exception e){
System.out.println(e);
}
if(s.contains("IRON"))
System.out.println("I found IRON");
}
Output:
I found IRON
My File content
BULLET
1
AE 1688
CHEERS
GAMES
IRON MAN
WOLF
Testing
Wonderful
Related
Write a program that asks a user to input a string. Then asks a user to type in an index value(integer). You will use the charAt( ) method from the string class to find and output the character referenced by that index. Allow the user to repeat these actions by placing this in a loop until the user gives you an empty string. Now realize that If we call the charAt method with a bad value (a negative value or a integer larger than the size of the string) an exception will be thrown. Add the code to catch this exception, output a warning message and then continue with the loop
import java.util.Scanner;
class Main
{
public static void main(String[] args)
{
System.out.println("");
String s;
int ind;
Scanner sc=new Scanner(System.in);
while(sc.hasNext())
{
s=sc.next();
if(s.length()==0)
break;
ind=sc.nextInt();
try {
char ch=s.charAt(ind);
System.out.println("Character is "+ch);
}
catch(Exception e) {
System.out.println("Bad index Error!");
}
}
}
}
Yes. You could rely on assignment evaluating to the assigned value. Also, call Scanner.hasNextInt() before calling Scanner.nextInt(). Like,
System.out.println();
String s;
Scanner sc = new Scanner(System.in);
while (sc.hasNext() && !(s = sc.next()).isEmpty()) {
if (sc.hasNextInt()) {
int ind = sc.nextInt();
try {
char ch = s.charAt(ind);
System.out.println("Character is " + ch);
} catch (Exception e) {
System.out.println("Bad index Error!");
}
}
}
There is a bug; sc.next() cannot return an empty string in this code. Try editing it this way:
while(sc.hasNext()) {
s = sc.next();
if(s.length() == 0) {
System.out.println("Woah, Nelly!");
break;
}
// ...
}
See if you can get the program to print "Woah, Nelly!" by entering a blank line, or anything else. I can't, and assuming I understand the documentation correctly, it is impossible for the if condition to ever be true here (emphasis mine):
Depending upon the type of delimiting pattern, empty tokens may be returned. For example, the pattern "\\s+" will return no empty tokens since it matches multiple instances of the delimiter. The delimiting pattern "\s" could return empty tokens since it only passes one space at a time.
This pattern "\\s+" is the default one, and you haven't set a different one, so your scanner should never return an empty token. So the strict answer to "is there a way to write this program without the break statement?" is: yes, you can just delete the if(...) break; code and it doesn't change the behaviour in any way.
However, that's not really a solution to your problem because it doesn't give the user a way to exit the program. You should use nextLine() instead of next() to allow reading a blank line from the user.
I'm kinda new to Java so I'm looking for an help to do this.
As the title says, I'm trying to write a program that checks if a number given by the user from console is inside a text file with one number for each line or not.
I am using the Scanner class to check every line, but I am having problems with what condition the if statement should have when the number is found inside the file.
I wrote down this part code (I'm not even sure if it's correct itself, so correct me if I'm wrong):
int lines = 0;
while (filescanner.hasNextLine()) {
String line = filescanner.nextLine();
lines++;
if(conditon here) {
System.out.println("I found the number on line " + lines);
}
}
Thanks in advance.
Since you are getting the input number from Scanner keyboard, you can get its value like this:
String input = keyboard.next();
Then your if condition can be if(line.contains(input))
You need to convert the line to an integer and then test it. If it is not an integer the parseInt method throws an exception.
try {
int n = Integer.parseInt(line);
if (n == number) {
// found it
}
} catch (NumberFormatException e) {
// Not a number
}
Hi I wanted to know how to write up a try and catch block to stop from getting the below error.
java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
I have this method which takes a sentence and splits it into an ArrayList. I then use that to store values into a hashmap, where index 1 is the key and the words after become the value. I use the below method to split the user input into an array.
private Scanner reader;
/**
* Create a new InputReader that reads text from the text terminal.
*/
public InputReader()
{
reader = new Scanner(System.in);
}
public ArrayList<String> getInput()
{
System.out.print("> "); // print prompt
String inputLine = reader.nextLine().trim().toLowerCase();
String[] wordArray = inputLine.split(" "); // split at spaces
// add words from array into ArrayList
ArrayList<String> words = new ArrayList<String>();
for(String word : wordArray) {
words.add(word);
}
return words;
}
}
and the below method uses the class above to detect user input. So when the user types in write they can write into a hashmap but if they press return before they type in a key and value I get the out of bounds exception. So How can i rewrite the below method to avoid this?
public void start()
{
boolean finished = false;
printWelcome();
while(!finished) {
ArrayList<String> input = reader.getInput();
if(input.contains("shutdown")) {
finished = true;
}
if (input.contains("load")) {
System.out.println();
instruct.readAndFill();
System.out.println();
}
if (input.contains("write")) {
String key = input.get(1);
String value = "";
for(int i=2; i<input.size(); i++) {
value = value + " " + input.get(i);
}
instruct.mapWrite(key, value);
}
}
instructorGoodBye();
}
Sorry if i wasn't clear enough, or if my code is not up to scratch i have only been learning java for about 2 months now.
basically if the user types in write key value on one line it is fine but if they hit return after write then the error happens.
So, fundamentally what you are missing is error checking. Your program is taking input from a user, and assuming it is valid. This is always a bad idea.
Instead, you should validate what you get from the user. One way you can do this, for your "write" block, is to make sure the elements you expect to be there, are actually there.
To start, I would rewrite your loop as follows:
while(!finished) {
List<String> input = reader.getInput();
if(input.size() == 0) {
throw new IllegalArgumentException("Must specify command, one of 'shutdown', 'load', 'write'");
}
final String command = input.remove(0).toLowerCase();
// TODO: Make sure command is one of the valid commands!
Note the changes:
Assigning to List instead of ArrayList is just a good general practice.
Checking the input to make sure it has more than zero elements
Taking the first element, since we don't want to have to do List.contains(). Consider the input garbage garbage garbage write, clearly we don't want this to invoke the "write" command, it should be considered invalid input.
Finally, we use this to rewrite the conditions on executing our commands:
if(command.equals("write")) {
// Make sure the user put the right stuff in here
// Since we removed the command from the input already, just make sure what is left is
if(input.size() <= 1) {
throw new IllegalArgumentException("Must specify correct data");
}
String key = input.remove(0);
String value = String.join(" ", input); // Java 8
instruct.mapWrite(key, value);
}
You are getting the error for below part of the code..
if (input.contains("write")) {
String key = input.get(1);// here is the problem..
String value = "";
for(int i=2; i<input.size(); i++) {
value = value + " " + input.get(i);
}
instruct.mapWrite(key, value);
}
in the line 2 of this code snippet. you are accessing a value by using the index. Now just imagine you just enter a single word in the console. so the arraylist you will get from the getInput() method will have the size of 1. So.. in the arraylist the word will be placed on 0th position.(that is the first position) but you are accessing the value on second position.. Thats gives you a index out of bond exception..
basically the fix was simpler than throwing a new exception and using a try and catch block. All I had to do was slightly change the logic and just use and if else statement.
if (input.contains("write")) {
if(input.size() >=2) {
String key = input.get(1);
String value = "";
for(int i=2; i<input.size(); i++) {
value = value + " " + input.get(i);
}
mapWrite(key, value);
} else {
System.out.println("Please type in the key & value after write all on line");
}
}
From what I have learned from java so far, is that the best solutions are normally always normally the simplest. Thanks for all the help, everyone who commented and tried to help me basically helped me come up with the idea.
I am writing a method to search through a dicitionary to find multiple words of the same length that contain the same letter at a set point. I.e. All words of length 5 that have b as their second letter.
I'm writing this method by TDD is eclipse and so far my method is as follows:
private OpenQueue openQueue = new OpenQueue();
private boolean value;
private int lengthOfWord, numberFound;
private File inFile = new File("src/src/WordList"); //This is a text file
public Search(int length) {
this.lengthOfWord = length;
}
public boolean examine2(int crossingPoint, char letter) {
try {
Scanner input = new Scanner(inFile);
while (input.hasNextLine()) { //while there are words left to be read
String word = input.nextLine();
if(word.length() == lengthOfWord) { //if the word is of the right length
while(word.charAt(crossingPoint-1) == letter){
numberFound = numberFound + 1; //number of solutions is increased by one
openQueue.add(word);//word is added to the open queue
value = true; //value is true when at least one solution has been found
}
}
}
} catch (FileNotFoundException e) {
System.out.println("They File was not Found");
e.printStackTrace();
}
System.out.println(numberFound); //returns number of words found
return value; //should return true if there is at least one word
}
For my test I trying to find all five letter words that have a second letter b and there are several words that fit this as I've checked manually. However when I run JUnit it says that it expected true but it was false.
The code runs up to but not past the while(word.charAt(crossingPoint-1) == letter) loop, as previously I added in System.out.println("Here") before this loop to check were the code runs until.
I'm not sure how to fix this in order for the code to run without the test failing. Thanks for your help.
It's hard to look at this code -- arghh! But there appear to be at least one syntax error. I'm not sure whether you just copied it into this question incorrectly, otherwise I don't even see how it can compile. You put parentheses after lengthOfWord which makes it look like a no-argument method or method call, but you appear to want to use it as an integer variable.
Also inFile and numberFound do not appear to be defined. You will have to provide more context.
I'm reading a text file line by line and converting it into a string.
I'm trying to figure out how to check if the last line of the file is a specific word ("FILTER").
I've tried to use the endsWith(String) method of String class but it's not detecting the word when it appears.
Rather naive solution, but this should work:
String[] lines = fileContents.split("\n");
String lastLine = lines[lines.length - 1];
if("FILTER".equals(lastLine)){
// Do Stuff
}
Not sure why .endsWith() wouldn't work. Is there an extra newline at the end? (In which case the above wouldn't work). Do the cases always match?
.trim() your string before checking with endsWith(..) (if the file really ends with the desired string. If not, you can simply use .contains(..))
public static boolean compareInFile(String inputWord) {
String word = "";
File file = new File("Deepak.txt");
try {
Scanner input = new Scanner(file);
while (input.hasNext()) {
word = input.next();
if (inputWord.equals(word)) {
return true;
}
}
} catch (Exception error) {
}
return false;
}
With
myString.endsWith("FILTER")
the very last characters of the last line are checked. Maybe the method
myString.contains("FILTER")
is the right method for you? If you only want to check the last ... e.g.20 chars try to substring the string and then check for the equals method.