I am a beginner to java. I try to write a program to read a series of words from the command-line arguments, and find the index of the first match of a given word. Like user can enter "I love apple", and the given word is "apple". The program will display "The index of the first match of ‘apple’ is 2".
What I did so far does not work. Is it my way of storing the input into the string array not correct?
import java.util.Scanner;
public class test {
public static void main(String [] args) {
System.out.println("Enter sentence: ");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
int num=1;
String sentence[]=new String[num];
for(int i=0; i< num; i++) {
sentence[i] = input; // store the user input into the array.
num = num+1;
}
System.out.println("Enter the given words to find the index of its first match: ");
Scanner sc2 = new Scanner(System.in);
String key = sc2.next();
for(int j=0; j<num; j++) {
while (sentence[j].equals(key)) {
System.out.println("The index of the first match of "+key+" is "+j);
}
}
}
}
String array is not required in your solution.
Try this :-
System.out.println("enter sentence ");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
System.out.println("enter the given word to fin the index ");
sc = new Scanner(System.in);
String toBeMatched = sc.nextLine();
if (input.contains(toBeMatched)) {
System.out.println("index is " + input.indexOf(toBeMatched));
} else {
System.out.println("doesn't contain string");
}
I have made the following changes to make your code work. Note you were storing the input string incorrectly. In your code, the entire code was being stored as the first index in the array. You don't need the first for-loop as we can use the function .split() to distinguish each word into a different index in the array. Rest of the code stays as it is.
public class ConfigTest {
public static void main(String[] args) {
System.out.println("Enter sentence: ");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
// Use this to split the input into different indexes of the array
String[] sentence = input.split(" ");
System.out.println("Enter the given words to find the index of its first match: ");
Scanner sc2 = new Scanner(System.in);
String key = sc2.next();
for (int i = 0; i < sentence.length; i++) {
if (sentence[i].equals(key)) {
System.out.println("The index of the first match of " + key + " is " + i);
}
}
}
}
I think you have a scope problem. sentence[] is declared and instantiated in your first forloop. Try moving the declaration outside of the loop and you should do away with the error.
I also noticed a couple of errors. You could try this
public static void main(String[] args) {
// TODO code application logic here
System.out.println("Enter Sentence");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
String sentence[] = input.split("\\s");
System.out.println("Enter Word");
Scanner sc2 = new Scanner(System.in);
String key = sc2.next();
int index = 0;
for(String word : sentence)
{
if(word.equals(key))
{
System.out.println("The index of the first match of " + key + " is " + index);
break;
}
index++;
}
}
Turtle
sentence variable is only defined inside the for loop, it needs to be declared outside it
You can use the first Scanner (sc) declared variable again instead of declaring another one (sc2)
sentence[i] = input -- will mean -- sentence[0] = "I love apple"
Scanner variable can do all the work for you for the input into the array instead of a for loop
String[] a = sc. nextLine(). split(" ");
This will scan an input of new line and separate each string separated by a space into each array.
System.out.println("Enter sentence: ");
Scanner sc = new Scanner(System.in);
String[] sentence = sc. nextLine(). split(" ");
System.out.println("Enter the given words to find the index of its first match: ");
String key = sc.nextLine();
for(int j=0; j<num; j++) {
if (sentence[j].matches(key)) {
System.out.println("The index of the first match of "+ key +" is "+ j);
}
}
Declare the String [] sentence outside the for loop. It is not visible outside the first for block.
The sentence array is created over and over again during the iteration of the for loop. The loop is not required to get the String from the command line.
Edited my answer and removed the use of any for loops, Arrays.asList() will take the words array and fetch the index of the word from the resulting List.
public static void main(String[] args) throws IOException {
System.out.println("Enter sentence: ");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
System.out.println("Enter the given word to find the index of its first match: ");
Scanner wordInput = new Scanner(System.in);
String key = wordInput.next();
String[] words = input.split(" ");
int occurence = Arrays.asList(words).indexOf(key);
if(occurence != -1){
System.out.println(String.format("Index of first occurence of the word is %d", occurence));
}
}
You just need to declare sentence array outside the for loop, as for now, the issue is of scope.For more on the scope of a variable in java . Also, this is not you intend to do, you intended to take input as a command line.
So, the input which you will get will come in String[] args. For more on command line arguments check here.
I am trying to get the strings to separate, and WITHOUT the comma.
We haven't learned anything like arrays, this is an intro class.
Everything I find on here just keeps giving me errors or does nothing to my code in zybooks.
import java.util.Scanner;
public class ParseStrings {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in); // Input stream for standard input
Scanner inSS = null; // Input string stream
String lineString = ""; // Holds line of text
String firstWord = ""; // First name
String secondWord = ""; // Last name
boolean inputDone = false; // Flag to indicate next iteration
// Prompt user for input
System.out.println("Enter input string: ");
// Grab data as long as "Exit" is not entered
while (!inputDone) {
// Entire line into lineString
lineString = scnr.nextLine();
inSS = new Scanner(lineString);
firstWord = inSS.next();
lineString.split(",");
// Output parsed values
if (firstWord.equals("q")) {
System.out.println("Enter input string: ");
inputDone = true;
}
//This may be where I am messing up??
else if (lineString.contains(",")) {
secondWord = inSS.next();
System.out.println("First word: " + firstWord);
System.out.println("Second word: " + secondWord);
System.out.println();
} else {
System.out.println("Error: No comma in string");
System.out.println("Enter input string: ");
}
}
return;
}
}
I am messing up somewhere and keep getting different error codes as I keep messing with it...
"Enter input string:
First word: Jill,
Second word: Allen"
When it should be
"Enter input string:
First word: Jill
Second word: Allen"
And then also as the computer enters more data I start getting this message:
"Exception in thread "main" java.util.NoSuchElementException"
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1371)
at ParseStrings.main(ParseStrings.java:44)"
One of the possibilities (if you didn't learn about arrays) is to use StringBuilder and remove commas or simply loop over input string and if character at let's say index 8 is comma, you do yourString.substring(0,8);, and then print the second word as yourString.substring(10, yourstring.length); I put starting index of 10 in the second substring because you want to skip comma and a space that's separating first and last name. Here is code sample for using nothing but String class, it's methods and for loop:
package com.company;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter first name and last name: ");
String str = in.nextLine();
int indexOfComma = 0;
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) == ',')
indexOfComma = i;
}
System.out.println("First name is: " + (str.substring(0, indexOfComma)));
System.out.println("Last name is: " + (str.substring(indexOfComma + 2, str.length())));
}
}
Or as I see you tried using split() (but since you said you didn't learn arrays yet I posted solution above), you can do it with .split() like this:
package com.company;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter first name and last name: ");
String[] name = in.nextLine().split(", ");
System.out.println("First name is: " + name[0]);
System.out.println("Last name is: " + name[1]);
}
}
Also, here is an example with StringBuilder class:
package com.company;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter first name and last name: ");
StringBuilder name = new StringBuilder(in.nextLine());
name.deleteCharAt(name.indexOf(","));
System.out.println("Full name is: " + name);
}
}
Your error happens when the Scanner reads all the data, such as calling the nextLine method and there's no line... Or next method when you didn't put a space after the comma
By default, the Scanner uses whitespace as a delimiter. If you want to add a comma delimiter before any whitespace, you can try this
Scanner sc=new Scanner(System.in);
sc.useDelimiter(",?\\s+");
Now, sc.next() will read only Hello from Hello, World, and a second call to it should return World
Or you can use the array you made
String[] words = lineString.split(",");
String first = words[0]:
String second = words[1];
How could I read input from the console using the Scanner class? Something like this:
System.out.println("Enter your username: ");
Scanner = input(); // Or something like this, I don't know the code
Basically, all I want is have the scanner read an input for the username, and assign the input to a String variable.
A simple example to illustrate how java.util.Scanner works would be reading a single integer from System.in. It's really quite simple.
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();
To retrieve a username I would probably use sc.nextLine().
System.out.println("Enter your username: ");
Scanner scanner = new Scanner(System.in);
String username = scanner.nextLine();
System.out.println("Your username is " + username);
You could also use next(String pattern) if you want more control over the input, or just validate the username variable.
You'll find more information on their implementation in the API Documentation for java.util.Scanner
Scanner scan = new Scanner(System.in);
String myLine = scan.nextLine();
Reading Data From The Console
BufferedReader is synchronized, so read operations on a BufferedReader can be safely done from multiple threads. The buffer size may be specified, or the default size(8192) may be used. The default is large enough for most purposes.
readLine() « just reads data line by line from the stream or source. A line is considered to be terminated by any one these: \n, \r (or) \r\n
Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace(\s) and it is recognised by Character.isWhitespace.
« Until the user enters data, the scanning operation may block, waiting for input.
« Use Scanner(BUFFER_SIZE = 1024) if you want to parse a specific type of token from a stream.
« A scanner however is not thread safe. It has to be externally synchronized.
next() « Finds and returns the next complete token from this scanner.
nextInt() « Scans the next token of the input as an int.
Code
String name = null;
int number;
java.io.BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
name = in.readLine(); // If the user has not entered anything, assume the default value.
number = Integer.parseInt(in.readLine()); // It reads only String,and we need to parse it.
System.out.println("Name " + name + "\t number " + number);
java.util.Scanner sc = new Scanner(System.in).useDelimiter("\\s");
name = sc.next(); // It will not leave until the user enters data.
number = sc.nextInt(); // We can read specific data.
System.out.println("Name " + name + "\t number " + number);
// The Console class is not working in the IDE as expected.
java.io.Console cnsl = System.console();
if (cnsl != null) {
// Read a line from the user input. The cursor blinks after the specified input.
name = cnsl.readLine("Name: ");
System.out.println("Name entered: " + name);
}
Inputs and outputs of Stream
Reader Input: Output:
Yash 777 Line1 = Yash 777
7 Line1 = 7
Scanner Input: Output:
Yash 777 token1 = Yash
token2 = 777
There is problem with the input.nextInt() method - it only reads the int value.
So when reading the next line using input.nextLine() you receive "\n", i.e. the Enter key. So to skip this you have to add the input.nextLine().
Try it like that:
System.out.print("Insert a number: ");
int number = input.nextInt();
input.nextLine(); // This line you have to add (it consumes the \n character)
System.out.print("Text1: ");
String text1 = input.nextLine();
System.out.print("Text2: ");
String text2 = input.nextLine();
There are several ways to get input from the user. Here in this program we will take the Scanner class to achieve the task. This Scanner class comes under java.util, hence the first line of the program is import java.util.Scanner; which allows the user to read values of various types in Java. The import statement line should have to be in the first line the java program, and we proceed further for code.
in.nextInt(); // It just reads the numbers
in.nextLine(); // It get the String which user enters
To access methods in the Scanner class create a new scanner object as "in". Now we use one of its method, that is "next". The "next" method gets the string of text that a user enters on the keyboard.
Here I'm using in.nextLine(); to get the String which the user enters.
import java.util.Scanner;
class GetInputFromUser {
public static void main(String args[]) {
int a;
float b;
String s;
Scanner in = new Scanner(System.in);
System.out.println("Enter a string");
s = in.nextLine();
System.out.println("You entered string " + s);
System.out.println("Enter an integer");
a = in.nextInt();
System.out.println("You entered integer " + a);
System.out.println("Enter a float");
b = in.nextFloat();
System.out.println("You entered float " + b);
}
}
import java.util.Scanner;
public class ScannerDemo {
public static void main(String[] arguments){
Scanner input = new Scanner(System.in);
String username;
double age;
String gender;
String marital_status;
int telephone_number;
// Allows a person to enter his/her name
Scanner one = new Scanner(System.in);
System.out.println("Enter Name:" );
username = one.next();
System.out.println("Name accepted " + username);
// Allows a person to enter his/her age
Scanner two = new Scanner(System.in);
System.out.println("Enter Age:" );
age = two.nextDouble();
System.out.println("Age accepted " + age);
// Allows a person to enter his/her gender
Scanner three = new Scanner(System.in);
System.out.println("Enter Gender:" );
gender = three.next();
System.out.println("Gender accepted " + gender);
// Allows a person to enter his/her marital status
Scanner four = new Scanner(System.in);
System.out.println("Enter Marital status:" );
marital_status = four.next();
System.out.println("Marital status accepted " + marital_status);
// Allows a person to enter his/her telephone number
Scanner five = new Scanner(System.in);
System.out.println("Enter Telephone number:" );
telephone_number = five.nextInt();
System.out.println("Telephone number accepted " + telephone_number);
}
}
You can make a simple program to ask for the user's name and print whatever the reply use inputs.
Or ask the user to enter two numbers and you can add, multiply, subtract, or divide those numbers and print the answers for user inputs just like the behavior of a calculator.
So there you need the Scanner class. You have to import java.util.Scanner;, and in the code you need to use:
Scanner input = new Scanner(System.in);
input is a variable name.
Scanner input = new Scanner(System.in);
System.out.println("Please enter your name: ");
s = input.next(); // Getting a String value
System.out.println("Please enter your age: ");
i = input.nextInt(); // Getting an integer
System.out.println("Please enter your salary: ");
d = input.nextDouble(); // Getting a double
See how this differs: input.next();, i = input.nextInt();, d = input.nextDouble();
According to a String, int and a double varies the same way for the rest. Don't forget the import statement at the top of your code.
A simple example:
import java.util.Scanner;
public class Example
{
public static void main(String[] args)
{
int number1, number2, sum;
Scanner input = new Scanner(System.in);
System.out.println("Enter First multiple");
number1 = input.nextInt();
System.out.println("Enter second multiple");
number2 = input.nextInt();
sum = number1 * number2;
System.out.printf("The product of both number is %d", sum);
}
}
When the user enters his/her username, check for valid entry also.
java.util.Scanner input = new java.util.Scanner(System.in);
String userName;
final int validLength = 6; // This is the valid length of an user name
System.out.print("Please enter the username: ");
userName = input.nextLine();
while(userName.length() < validLength) {
// If the user enters less than validLength characters
// ask for entering again
System.out.println(
"\nUsername needs to be " + validLength + " character long");
System.out.print("\nPlease enter the username again: ");
userName = input.nextLine();
}
System.out.println("Username is: " + userName);
To read input:
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
To read input when you call a method with some arguments/parameters:
if (args.length != 2) {
System.err.println("Utilizare: java Grep <fisier> <cuvant>");
System.exit(1);
}
try {
grep(args[0], args[1]);
} catch (IOException e) {
System.out.println(e.getMessage());
}
import java.util.*;
class Ss
{
int id, salary;
String name;
void Ss(int id, int salary, String name)
{
this.id = id;
this.salary = salary;
this.name = name;
}
void display()
{
System.out.println("The id of employee:" + id);
System.out.println("The name of employye:" + name);
System.out.println("The salary of employee:" + salary);
}
}
class employee
{
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
Ss s = new Ss(sc.nextInt(), sc.nextInt(), sc.nextLine());
s.display();
}
}
Here is the complete class which performs the required operation:
import java.util.Scanner;
public class App {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
final int valid = 6;
Scanner one = new Scanner(System.in);
System.out.println("Enter your username: ");
String s = one.nextLine();
if (s.length() < valid) {
System.out.println("Enter a valid username");
System.out.println(
"User name must contain " + valid + " characters");
System.out.println("Enter again: ");
s = one.nextLine();
}
System.out.println("Username accepted: " + s);
Scanner two = new Scanner(System.in);
System.out.println("Enter your age: ");
int a = two.nextInt();
System.out.println("Age accepted: " + a);
Scanner three = new Scanner(System.in);
System.out.println("Enter your sex: ");
String sex = three.nextLine();
System.out.println("Sex accepted: " + sex);
}
}
There is a simple way to read from the console.
Please find the below code:
import java.util.Scanner;
public class ScannerDemo {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
// Reading of Integer
int number = sc.nextInt();
// Reading of String
String str = sc.next();
}
}
For a detailed understanding, please refer to the below documents.
Doc
Now let's talk about the detailed understanding of the Scanner class working:
public Scanner(InputStream source) {
this(new InputStreamReader(source), WHITESPACE_PATTERN);
}
This is the constructor for creating the Scanner instance.
Here we are passing the InputStream reference which is nothing but a System.In. Here it opens the InputStream Pipe for console input.
public InputStreamReader(InputStream in) {
super(in);
try {
sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## Check lock object
}
catch (UnsupportedEncodingException e) {
// The default encoding should always be available
throw new Error(e);
}
}
By passing the System.in this code will opens the socket for reading from console.
You can flow this code:
Scanner obj= new Scanner(System.in);
String s = obj.nextLine();
You can use the Scanner class in Java
Scanner scan = new Scanner(System.in);
String s = scan.nextLine();
System.out.println("String: " + s);
import java.util.Scanner; // Import the Scanner class
class Main { // Main is the class name
public static void main(String[] args) {
Scanner myObj = new Scanner(System.in); // Create a Scanner object
System.out.println("Enter username");
String userName = myObj.nextLine(); // Read user input
System.out.println("Username is: " + userName); // Output user input
}
}
you have wrote
Scanner = input()
this is wrong method, you have to make an integer or a string, i would like to prefer string, and then give a string any name that can be i that can be n or anything else, remember that you are giving name to username you can also give name username also, and the code is
String username = sc.nextline();
System.our.println("the username is" + username);
I hope you understand now
How do you "delete" a character from a file. Also, how do you print the stuff in the file out?
Write a program that reads in a file of text, perhaps the text of a novel. The program copies the same text to an output file, except that all the useless words such as "the", "a", and "an" are removed. (Decide on what other words you with to remove. The list of words removed is called a stop list.) Do this by reading the text file token by token using hasNext() and next(), but only writing out tokens not on the stop list.
Prompt the user for the names of the input and output files. Preserve the line structure of the input file. Do this by reading each line using nextLine() and then creating a new Scanner for that line. (Look at the on-line documentation for Scanner.) With each line's Scanner, use hasNext() and next() to scan through its tokens.
public static void main(String[] args) throws IOException {
String fileName;
Scanner user = new Scanner(System.in);
System.out.print("File name: ");
fileName = user.nextLine().trim();
File file = new File(fileName);
PrintStream printfile = new PrintStream(file);
System.out.println("Input data into file: ");
String datainfile = user.nextLine();
Scanner scan = new Scanner(file);
printfile.println(datainfile);
while (scan.hasNextLine()) {
while (scan.hasNext()) {
String character = scan.next();
if (character.equals("a")) {
}
}
}
}
EDIT
thanks to peeskillet I tried attempting again. However, there seems to be an error somewhere in my program and I get:
AAApotatopotatopotatojava.util.Scanner[delimiters=\p{javaWhitespace}+][position=0] [match valid=false][need input=false][source closed=false][skipped=false][group separator=\,][decimal separator=\.][positive prefix=][negative prefix=\Q-\E][positive suffix=][negative suffix=][NaN string=\Q�\E][infinity string=\Q∞\E]
Can you inspect my program?
public static void main(String[] args) throws IOException {
Scanner keyboard = new Scanner(System.in);
System.out.print("Input File name: ");
String filename1 = keyboard.nextLine().trim();
System.out.print("Output File name: ");
String filename2 = keyboard.nextLine().trim();
File inputFile = new File(filename1);
File outputFile = new File(filename2);
PrintStream printfile = new PrintStream(inputFile);
System.out.println("Input data into file: ");
String datainfile = keyboard.nextLine();
printfile.println(datainfile);
Scanner inFile = new Scanner(inputFile);
PrintWriter writeFile = new PrintWriter(outputFile);
Scanner lineScanner;
while (inFile.hasNextLine()) {
String line = inFile.nextLine();
lineScanner = new Scanner(line);
while (lineScanner.hasNext()) {
String word = lineScanner.next();
if(!(word.equals("a"))) {
writeFile.print(word + " ");
System.out.print(word);
}
if(!(word.equals("an"))) {
writeFile.print(word + " ");
System.out.print(word);
}
if(!(word.equals("the"))) {
writeFile.print(word + " ");
System.out.print(word);
}
else {
writeFile.print(" ");
}
}
writeFile.println();
}
writeFile.close();
Scanner readOutput = new Scanner(outputFile);
System.out.println(readOutput);
}
}
First of all you need two File objects, one for input and one for output. You only have one.
You want to do something like this
Scanner keyboard = new Scanner(System.in);
System.out.print("Input File name: ");
String filename1 = keyboard.nextLine();
System.out.print("Output File name: ");
String filename2 = keyboard.nextLine();
File inputFile = new File(filename1);
File outputFile = new File(filename2);
Scanner infile = new Scanner(inputFile);
PrintWriter outputFile = new PrintWriter(outputFile);
Scanner lineScanner;
while(infile.hasNextLine()){ // here you read each line of a file
String line = inFile.nextLine(); // here is a line
lineScanner = new Scanner(line); // for the above line, create a scanner
// just to scan that line
while(lineScanner.hasNext()){ // loop through that line
// do something
}
}
outputFile.close();
Edit: I would just put all the conditions into one statement
while (lineScanner.hasNext()) {
String word = lineScanner.next();
if(!(word.equals("a")) && !(word.equals("an")) && !(word.equals("the"))) {
writeFile.print(word + " ");
System.out.print(word);
}
}
I am trying to write a little program that will use scanner to check if there is a next line (in awhile loop) and then maybe another one to check that the words on the line are tab appart and there are 3 strings (the use constructor to create a object) so the three strings would be Product Name Manufacturer Brcode
EG: Tyre17x60 Goodyear 458765464
and so and so
I am bit stuck with this so any help would be grateful
You can try this:
public static void main (String[] args) throws java.lang.Exception
{
String str = "Tyre17x60 Goodyear 458765464";
InputStream is = new ByteArrayInputStream(str.getBytes());
Scanner sc = new Scanner(is);
sc.useDelimiter("\n");
while (sc.hasNext())
{
String[] tmp = sc.next().split("\t");
if (tmp.length == 3)
System.out.println("Text contains 3 parts separated with tabs");
else
System.out.println("Text is not well formated");
// save data
//productName = tmp[0];
//manufacturer = tmp[1];
//brcode = tmp[2];
}
}
Assuming you are reading from a file, you can use the following code:
Scanner s = new Scanner(new File("file.txt"));
while(s.hasNext())
{
String productName = s.next();
String Manufacturer = s.next();
String Brcode = s.next();
}
Scanner scan = new Scanner("file.txt");
while(scan.hasNext()){
scan.nextLine();
System.out.println("Product : " + scan.next());
System.out.println("Name : " + scan.next());
System.out.println("Code : " + scan.nextLong());
}
Try something like this....