Develop Reference

Using Scanner and Arrays's to add BigInts

This is a project from school, but i'm only asking for help in the logic on one small part of it. I got most of it figured out.
I'm being given a file with lines of string integers, for example:
1234 123
12 153 23
1234
I am to read each line, compute the sum, and then go to the next one to produce this:
1357
188
1234
I'm stuck on the scanner part.
public static void doTheThing(Scanner input) {
int[] result = new int[MAX_DIGITS];
while(input.hasNextLine()) {
String line = input.nextLine();
Scanner linesc = new Scanner(line);
while(linesc.hasNext()) {
String currentLine = linesc.next();
int[] currentArray = convertArray(stringToArray(currentLine));
result = addInt(result, currentArray);
}
result = new int[MAX_DIGITS];
}
}
In a nutshell, I want to grab each big integer, put it an array of numbers, add them, and then i'll do the rest later.
What this is doing it's basically reading all the lines and adding everything and putting it into a single array.
What i'm stuck on is how do I read each line, add, reset the value to 0, and then read the next line? I've been at this for hours and i'm mind stumped.
Edit 01: I realize now that I should be using another scanner to read each line, but now i'm getting an error that looks like an infinite loop?
Edit 02: Ok, so after more hints and advice, I'm past that error, but now it's doing exactly what the original problem is.
Final Edit: Heh....fixed it. I was forgetting to reset the value to "0" before printing each value. So it makes sense that it was adding all of the values.
Yay....coding is fun....

hasNext method of the Scanner class can be used to check if there is any data available in stream or not. Accordingly, next method used to retrieve next continuous sequence of characters without white space characters. Here use of the hasNext method as condition of if doesn't make any sense as what you want is to check if the there are any numerical data left in the current line. You can use next(String pattern).
In addition, you can try this solution even though it is not optimal solution...
// In a loop
String line = input.nextLine(); //return entire line & descard newline character.
String naw[] = line.split(" "); //split line into sub strings.
/*naw contains numbers of the current line in form of string array.
Now you can perfom your logic after converting string to int.*/
I would also like to mention that it can easily & efficiently be done using java-8 streams.

An easier approach would be to abandon the Scanner altogether, let java.nio.io.Files to the reading for you and then just handle each line:
Files.lines(Paths.get("/path/to/my/file.txt"))
.map(s -> Arrays.stream(s.split("\\s+")).mapToInt(Integer::parseInt).sum())
.forEach(System.out::println);

If i were you i would be using the BufferedReader insted of the Scanner like this:
BufferedReader br = new BufferedReader(new FileReader("path"));
String line = "";
while((line = br.readLine()) != null)
{
int sum = 0;
String[] arr = line.split(" ");
for(String num : arr)
{
sum += Integer.parseInt(num);
}
System.out.println(sum);
}

Considering the level you're on, I think you should consider this solution. By using only the scanner, you can split the lines into an array of tokens, then iterate and sum the tokens by parsing them and validating that they're not empty.
import java.util.*;
class SumLines {
public static void main(String[] args) {
Scanner S = new Scanner(System.in);
while(S.hasNext()) {
String[] tokens = S.nextLine().split(" ");
int sum = 0;
for(int i = 0; i < tokens.length; i++) {
if(!tokens[i].equals("")) sum += Integer.parseInt(tokens[i]);
}
System.out.println(sum);
}
}
}

A java program to find out the frequrncy of a word using Scanner class

Can any one tell me that how to use Scanner Class of Java to find the frequency of a word in a sentence.
I am confused as to enter a line in java i have to use nextInt() function but to compare need it to convert in char so how to do so.
For example:-
I enter on terminal window(Giving Input)
This is my cat.
Now i have to find the FREGUENCY of word "this" in the above sentence. Please can you give me some idea.REMEMBER THE RESTRICTION IMPOSED ON IT IS I HAVE TO USE ONLY SCANNER CLASS OF JAVA LIBRARY
PROGRAMME USING STREAM READER IS AS FOLLOWS-
import java.io.*;
class FrequencyCount
{
public static void main(String args[]) throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the String: ");
String s=br.readLine();
System.out.println("Enter substring: ");
String sub=br.readLine();
int ind,count=0;
for(int i=0; i+sub.length()<=s.length(); i++)
//i+sub.length() is used to reduce comparisions
{
ind=s.indexOf(sub,i);
if(ind>=0)
{
count++;
i=ind;
ind=-1;
}
}
System.out.println("Occurence of '"+sub+"' in String is "+count);
}
}

alternative solution using pattern
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class JavaApplication20 {
public static void main(String [] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a sentence:\t");
String sentence = scanner.nextLine();
System.out.print("Enter a word:\t");
String word = scanner.nextLine();
Pattern p = Pattern.compile(word);
Matcher m = p.matcher(sentence);
int count = 0;
while (m.find()){
count +=1;
}
System.out.println("in your sentence the frequency of \""+word+"\" is:\t" + count);
}
}

try out this.
public class JavaApplication20 {
public static void main(String [] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a sentence:\t");
String sentence = scanner.nextLine();
System.out.print("Enter a word:\t");
String word = scanner.nextLine();
int count = 0;
while (!sentence.equals("")){
if(sentence.contains(word)){ // check if the word is in the sentence; if yes cut the sentence at the index of the first appearance of the word plus word length
// then check the rest of the sentence for more appearances
sentence = sentence.substring(sentence.indexOf(word)+word.length());
count++;
}
else{
sentence = "";
}
}
System.out.println("in your sentence the frequency of \""+word+"\" is:\t" + count);
}
}

You can enter a String too using Scanner Class . Here is your code that i modified , and it working . `
public static void main(String args[]) throws IOException
{
Scanner in=new Scanner(System.in);
System.out.println("Enter the String: ");
String s=in.nextLine();
System.out.println("Enter substring: ");
String sub=in.nextLine();
int ind,count=0;
for(int i=0; i+sub.length()<=s.length(); i++)
//i+sub.length() is used to reduce comparisions
{
ind=s.indexOf(sub,i);
if(ind>=0)
{
count++;
i=ind;
ind=-1;
}
}
System.out.println("Occurence of '"+sub+"' in String is "+count);
}
The nextLine() method of Scanner class let you input Strings.

Don't listen to #Uzochi. His answers may work, but they're way too complicated and may actually slow your program down.
For the Scanner class, there are multiple ways of reading in numbers or text:
nextInt() - scans in the next integer value
nextDouble() - scans in the next double value
nextLine() - scans in the next line of text
https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html - scroll down to method summary, and in the middle of all of the methods, you will find all of the "next" methods.
Note that there is a small bug with Scanner (at least with the last time I used it). Say you're using a Scanner called scan. If you call
scan.nextInt();
scan.nextLine();
(which reads in an integer and then a line of text), your Scanner will skip the call to nextLine(). This is a small bug that can easily be fixed by adding another nextLine(). It will catch the second nextLine.
In response to #Uzochi, there is a much simpler solution to your algorithm. Your algorithm is actually faster than his, although there are some small things that could make your program run a tiny bit faster:
1) Use a while loop instead of a for loop. Your use of indexOf() makes the current index of the String s you're at skip forward a lot, so there's virtually no point in having a for loop. You can easily change it into a while loop. Your conditions would be to keep checking if indexOf() returns a non-negative value (-1 means there is no value), and you increment that index value by 1 (like the for loop does automatically).
2) Smaller thing - you don't need the line:
ind=-1;
Your current code will always modify ind before it hits that if statement, so there is virtually no reason to have this line in the program.
EDIT - #Uzochi may be using Java's built in libraries, but for a beginner like OP, you should be learning how to use for and while loops to efficiently write code.

Accumulate Strings in Loop and Print Out all of them

I am trying to figure out how to accumulate user inputs in for loop and then to print them out with one system.out.print. This is my test code for the problem.
So for example if a user type : Mike for his name and Joe,Jack,Dave for other names, how to print them all just having one variable because amount of variables are not known since a user has that decision. Also is it possible to do that without stringbuilder and without arrays?
import java.util.Scanner;
public class Accumulate {
public static void main(String[] args) {
String othernames = " ",name;
int count,n;
Scanner kybrd = new Scanner(System.in);
System.out.println("Enter your name ");
name = kybrd.nextLine();
System.out.println("How many other names would you like to add ? ");
count = kybrd.nextInt();
kybrd.nextLine();
for(n=0;n<count;++n){
System.out.println("Enter other names ");
othernames = kybrd.nextLine();
}
System.out.println("Other names are "+othernames + " And your name is "+ name);
}
}

You can call it recursively, for instance:
Scanner sc = new Scanner(System.in);
String s;
while(condition) {
s = s + sc.nextLine();
}
this will always concat the lines you enter, you can also add commas, or spaces, or whatever you want to add.

as for your question about using Objects other than StringBuilder you can use List<String> and build a string for it at the final step.
you can use Map<String, String> if you need more complex data structure.

How to take integer and remove other data types from the file java?

I do not know how to take the integer and ignore the strings from the file using scanner. This is what I have so far. I need to know how to read the file token by token. Yes, this is a homework problem. Thank you so much.
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ClientMergeAndSort{
public static void main(String[] args){
int length = 13;
try{
Scanner input = new Scanner(System.in);
System.out.print("Enter the file name with extention : ");
File file = new File(input.nextLine());
input = new Scanner(file);
while (!input.hasNextInt()) {
input.next();
}
int[] arraylist = new int[length];
for(int i =0; i < length; i++){
length++;
arraylist[i] = input.nextInt();
System.out.print(arraylist[i] + " ");
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}

Take a look at the API for what you're doing.
http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#hasNextInt()
Specifically, Scanner.hasNextInt().
"Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the nextInt() method. The scanner does not advance past any input."
So, your code:
while (!input.hasNextInt()) {
input.next();
}
That's going to look and see if input hasNextInt().
So if the next token - one character - is an int, it's false, and skips that loop.
If the next token isn't an int, it goes into the loop... and iterates to the next character.
That's going to either:
- find the first number in the input, and stop.
- go to the end of the input, not find any numbers, and probably hits an IllegalStateException when you try to keep going.
Write down in words what you want to do here.
Use the API docs to figure out how the hell to tell the computer that. :) Get one bit at a time right; this has several different parts, and the first one doesn't work yet.
Example: just get it to read a file, and display each line first. That lets you do debugging; it lets you build one thing at a time, and once you know that thing works, you build one more part on it.
Read the file first. Then display it as you read it, so you know it works.
Then worry about if it has numbers or not.

A easy way to do this is read all the data from file in a way that you prefer (line by line for example) and if you need to take tokens, you can use split function (String.split see Java doc) or StringTokenizer for each line of String that you are reading using a loop, in order to create tokens with a specific delimiter (a space for example) so now you have the tokens and you can do something that you need with them, hope you can resolve, if you have question you can ask.
Have a nice programming.

import static java.nio.file.Files.readAllBytes;
import static java.nio.file.Paths.get;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Test {
public static void main(String args[]) throws IOException {
String newStr=new String(readAllBytes(get("data.txt")));
Pattern p = Pattern.compile("-?\\d+");
Matcher m = p.matcher(newStr);
while (m.find()) {
System.out.println("- "+m.group());
}
}
}
This code fill read the file and then using the regular expression you can get only Integer values.
Note: This code works in Java 8

I Think This will work for you requirement.
Before reading the data from the file initially,try to write some content to the file by using scanner and filewriter then try to execute the below code snippet.
File file = new File(your filepath);
List<Integer> list = new ArrayList<Integer>();
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
String str =null;
while(true) {
str = bufferedReader.readLine();
if(str!=null) {
System.out.println(str);
char[] chars = str.toCharArray();
String finalInt = "";
for(int i=0;i<chars.length;i++) {
if(Character.isDigit(chars[i])) {
finalInt=finalInt+chars[i];
}
}
list.add(Integer.parseInt(finalInt));
System.out.println(list.size());
System.out.println(list);
} else {
break;
}
}
}catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
The final println statement will display all the integer in your file line by line.
Thanks

How to take a scanner object and make it a String

I need help doing the following:
receiving input using Scanner class (I got this)
taking input from scanner and making it a String
use replaceAll to remove numbers 0-9 from user input.
The below code is what I have so far but it is only returning user input and not removing numbers:
public static void main(String[] args) {
Scanner firstname = new Scanner(System.in);
System.out.println("Please enter your first name:");
String firstname1 = firstname.next();
firstname1.replaceAll("[^0-9]","");
System.out.println(firstname1);
Updated Code. Thank you Hovercraft. I am now investigating how to retrieve all alpha characters as with the code below, I am only getting back the letters prior to the numeric values entered by the user:
import java.util.Scanner;
public class Assignment2_A {
public static void main(String[] args) {
Scanner firstname = new Scanner(System.in);
System.out.println("Please enter your first name:");
String firstname1 = firstname.next();
firstname1 = firstname1.replaceAll("[^A-Z]","");
System.out.println(firstname1);

String input = yourScannerObject.nextLine ();
where "yourScannerObject" is the name you give your scanner.

What method did you use to scan? is it {scanner object name}.next() ?
if so you have got a string and all that you have to do is create some string, and save the input to it, e.g.:
String str="";
str = {scanner object name}.next();
before using anything in java, I would advise you to read the API :
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Scanner.html#next()

receiving input using Scanner class (I got this)
taking input from scanner and making it a String
use replaceAll to remove numbers 0-9 from user input.
Here's an example:
String in;
Scanner scan = new Scanner("4r1e235153a6d 6321414t435hi4s 4524str43i5n5g");
System.out.println(in = (scan.nextLine().replaceAll("[0-9]", ""))); // use .next() for space or tab
Output:
read this string
The problem in your code is the regex "[^A-Z]" is set to remove all non-alphabet capital characters. This means you remove all lower case as well. You could say "[^a-zA-Z]", but then you're also removing special characters.