I want to read this string (from console not file) for example:
one two three
four five six
seven eight nine
So I want to read it per line and put every line in an array.
How can I read it? Because if I use scanner, I can only read one line or one word (nextline or next).
what I mean is to read for example : one two trhee \n four five six \n seven eight nine...
You should do by yourself!
There is a similer example:
public class ReadString {
public static void main (String[] args) {
// prompt the user to enter their name
System.out.print("Enter your name: ");
// open up standard input
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String userName = null;
// read the username from the command-line; need to use try/catch with the
// readLine() method
try {
userName = br.readLine();
} catch (IOException ioe) {
System.out.println("IO error trying to read your name!");
System.exit(1);
}
System.out.println("Thanks for the name, " + userName);
}
} // end of ReadString class
To answer the question as clarified in the comment on the first answer:
You must call Scanner's nextLine() method once for each line you wish to read. This can be accomplished with a loop. The problem you will inevitably encounter is "How do I know big my result array should be?" The answer is that you cannot know if you do not specify it in the input itself. You can modify your programs input specification to require the number of lines to read like so:
3
One Two Three
Four Five
Six Seven Eight
And then you can read the input with this:
Scanner s = new Scanner(System.in);
int numberOfLinesToRead = new Integer(s.nextLine());
String[] result = new String[numberOfLinesToRead];
String line = "";
for(int i = 0; i < numberOfLinesToRead; i++) { // this loop will be run 3 times, as specified in the first line of input
result[i] = s.nextLine(); // each line of the input will be placed into the array.
}
Alternatively you can use a more advanced data structure called an ArrayList. An ArrayList does not have a set length when you create it; you can simply add information to it as needed, making it perfect for reading input when you don't know how much input there is to read. For example, if we used your original example input of:
one two trhee
four five six
seven eight nine
You can read the input with the following code:
Scanner s = new Scanner(System.in);
ArrayList<String> result = new ArrayList<String>();
String line = "";
while((line = s.nextLine()) != null) {
result.add(line);
}
So, rather than creating an array of a fixed length, we can simply .add() each line to the ArrayList as we encounter it in the input. I recommend you read more about ArrayLists before attempting to use them.
tl;dr: You call next() or nextLine() for each line you want to read using a loop.
More information on loops: Java Loops
Look at this code:
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class SearchInputText {
public static void main(String[] args) {
SearchInputText sit = new SearchInputText();
try {
System.out.println("test");
sit.searchFromRecord("input.txt");
System.out.println("test2");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private void searchFromRecord(String recordName) throws IOException {
File file = new File(recordName);
Scanner scanner = new Scanner(file);
StringBuilder textFromFile = new StringBuilder();
while (scanner.hasNext()) {
textFromFile.append(scanner.next());
}
scanner.close();
// read input from console, compare the strings and print the result
String word = "";
Scanner scanner2 = new Scanner(System.in);
while (((word = scanner2.nextLine()) != null)
&& !word.equalsIgnoreCase("quit")) {
if (textFromFile.toString().contains(word)) {
System.out.println("The word is on the text file");
} else {
System.out.println("The word " + word
+ " is not on the text file");
}
}
scanner2.close();
}
}
Related
I can't get my scanner to read in the integer from a text file.
The file looks something like this (a matrix size followed by a matrix)
3
0 1 1
1 1 1
1 0 0
These two methods belong to ReadMatrix
public void openFile() {
try {
scanner = new Scanner(System.in); // create a scanner object
System.out.println("File to read: ");
fileName = scanner.nextLine(); // get name of file
System.out.println("File " + fileName + " is opened.");
br = new BufferedReader(new FileReader(fileName));
} catch (Exception e) {
System.out.println("can't find the funky file");
}
}
public int readInteger() {
sc = new Scanner(System.in);
// while(sc.hasNextInt()){
// sc.nextLine();
anInt = sc.nextInt();
System.out.println("Trying to read integerrrrrr help");
// }
return anInt;
}
Here are 2 classes
public class MainMethodHere {
public static void main(String[] args) {
// TODO Auto-generated method stub
RunMainMethod running = new RunMainMethod();
}
}
public class RunMainMethod {
ReadMatrix a = new ReadMatrix();
public RunMainMethod(){
a.openFile();
a.createFile();
System.out.println("just createdFile"); //<--- this is where the program ends
a.readInteger();
System.out.println("just readInteger");
a.helpMeWrite();
System.out.println("Just write sample ");
a.closeResources();
}
}
Writing to the file works fine, but I can't get the program to read the given text file to start the manipulation.
I tried finding the solutions in a few SO posts: how to read Integer from a text file in Java
Reading numbers from a .txt file into a 2d array and print it on console
How to read integer values from text file
I also tried ReadFile() and WriteFile(), but when I try to track my code via printing into the console, my simple integers shows up as different values. Is that something related to bytes? So I try reverting back to using a scanner, but somehow it's not working. Please let me know if I should clarify something further. I am new to coding and SO.
I'm trying to read from a .java the methods I have on it, also the classes, I'm using taggs to identify them and stored them, the problem is that using BufferedReader sometimes just doesn't work, the buffer skips a lot of lines for a reason that I can't understand, sometimes when checking the file by myself I just put random spaces between lines, and that fixes some parts, but I can't get the Buffer read all my text without skipping anything, my code so far is like this:
public class ReadFile {
public static void main(String[] args) {
int numclas=0,numbase=0,numbaseagr=0,numbmet=0,numag=0;
String mt="//MT";
String[] nomclass2 = new String[10];
String[] nommetodo2 = new String[50];
boolean metodo=false;
BufferedReader in = null;
try {
in = new BufferedReader(new FileReader("\\Program.java"));
String read = null;
while ((read = in.readLine()) != null) {
read = in.readLine();
String[] splited = read.trim().split("\\s+");
for(int i=0;i<splited.length;i++){
System.out.println(splited[i]);
if(splited[i].equals("class")){
nomclass2[numclas]=splited[i+1];
numclas=numclas+1;
}
if (splited[i].equals(mt)){
metodo=true;
}
if (splited[i].equals("public")){
if (splited[i+1].equals("static")){
nommetodo2[numbmet]=splited[i+3];
numbmet=numbmet+1;
}
if (splited[i+1].equals("int")||splited[i+1].equals("double")||splited[i+1].equals("String")||splited[i+1].equals("boolean")){
nommetodo2[numbmet]=splited[i+2];
numbmet=numbmet+1;
}
if (splited[i].equals("int")||splited[i].equals("double")||splited[i].equals("String")||splited[i].equals("boolean")){
nommetodo2[numbmet]=splited[i+1];
numbmet=numbmet+1;
}
metodo=false;
}
if ((splited[i].equals("int")||splited[i].equals("double")||splited[i].equals("String")||splited[i].equals("boolean"))&&metodo){
nommetodo2[numbmet]=splited[i+1];
numbmet=numbmet+1;
metodo=false;
}
}
}
} catch (IOException e) {
System.out.println("There was a problem: " + e);
e.printStackTrace();
} finally {
try {
in.close();
} catch (Exception e) {
}
}
Now let me show you the .java I'm trying to read:
import java.text.DecimalFormat;
import java.io.*;
//Main file of the program 1
public class Program1 {
//MT
public static void main (String args []) {
DecimalFormat format=new DecimalFormat("##.##");
System.out.println("How many data do you want to insert?");
int num=Leer.Int();
Fila lista=new Fila();
Fila lista2=new Fila();
double x=0.0;
for(int i=0;i<num;i++){
x=Leer.Double();
lista.addNum(x);
}
double prom=0.0;
double desv=0.0;
prom=lista.getprom();
desv=lista.getdevst();
System.out.println("The mean for column 1 is: "+format.format(prom));
System.out.println("The Std.Dev for column 1 is: "+format.format(desv));
System.out.println("How many data do you want to insert?");
num=Leer.Int();
x=0.0;
for(int i=0;i<num;i++) {
x=Leer.Double();
lista2.addNum(x);
}
prom=0.0;
desv=0.0;
prom=lista2.getprom();
desv=lista2.getdevst();
System.out.println("The mean for column 2 is: "+format.format(prom));
System.out.println("The Std.Dev for column 2 is: "+format.format(desv));
}
}
And the result when I print the array
Date:
12/12/12
import
java.text.DecimalFormat;
//Main
file
of
the
program
1
//MT
DecimalFormat
format=new
DecimalFormat("##.##");
so on...
See how in the //MT the Buffer skips a lot of lines, a lot of this is happening (see how it ignores the first lines of the program), and I don't know how to fix it, because sometimes when I try to "fix it" and add some spaces in the lines, I get a nullpointer and the program ends.
Any help will be appreciated, thank you.
This is just a partial answer - at the very least your program is skipping every other line:
while ((read = in.readLine()) != null)
will read a line from the file. The line is immediately discarded because the immediately following statement:
read = in.readLine();
reads and processes the next line from the file.
(also, 'splited' should be 'splitted' along with numerous other spelling mistakes but they're not really affecting your program, just it's readability :-))
System.out.print("Enter some stuff:");
while (input.hasNext()){
System.out.print(input.next()+ " ");
}
Whenever this runs, it asks the user for input, then prints it all out. However, what I want, is a loop that will print out all of the tokens of a scanner. Then, it realizes there are no more tokens, and the loop exits.
Well, you'd want to read the tokens into an ArrayList, like this:
List<String> store = new ArrayList<String>();
// read them all in and add them to our list
while (input.hasNext())
store.add(input.next());
// now print them all out
for (String s: store)
System.out.print(s+ " ");
What this does is to read them all in, and put them into the ArrayList; then, the reading loop exits when there's nothing more to read. After that, it prints them all out. I think this is what you have in mind. If you wanted to print them while you were adding them, then you could
List<String> store = new ArrayList<String>();
// read them all in and add them to our list
while (input.hasNext()) {
String s = input.next();
store.add(s);
System.out.print(s+ " ");
}
for (String s: store) {
// do whatever you like with them
}
Don't just copy, try to understand mate:
import java.io.*;
import java.util.StringTokenizer;
public class PrintStuff {
public static void main (String[] args) {
System.out.print("Enter some shit seperated by space:");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String str="";
try {
str = br.readLine();
} catch (IOException ioe) {
System.out.println("IO error trying to read bitch!");
}
StringTokenizer st = new StringTokenizer(str);
while (st.hasMoreElements()) {
System.out.println(st.nextElement());
}
}
}
I am a noobie at programming and I can't seem to figure out what to do.
I am to write a Java program that reads in any number of lines from a file and generate a report with:
the count of the number of values read
the total sum
the average score (to 2 decimal places)
the maximum value along with the corresponding name.
the minimum value along with the corresponding name.
The input file looks like this:
55527 levaaj01
57508 levaaj02
58537 schrsd01
59552 waterj01
60552 boersm01
61552 kercvj01
62552 buttkp02
64552 duncdj01
65552 beingm01
I program runs fine, but when I add in
score = input.nextInt(); and
player = input.next();
The program stops working and the keyboard input seems to stop working for the filename.
I am trying to read each line with the int and name separately so that I can process the data and complete my assignment. I don't really know what to do next.
Here is my code:
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;
public class Program1 {
private Scanner input = new Scanner(System.in);
private static int fileRead = 0;
private String fileName = "";
private int count = 0;
private int score = 0;
private String player = "";
public static void main(String[] args) {
Program1 p1 = new Program1();
p1.getFirstDecision();
p1.readIn();
}
public void getFirstDecision() { //*************************************
System.out.println("What is the name of the input file?");
fileName = input.nextLine(); // gcgc_dat.txt
}
public void readIn(){ //*********************************************
try {
FileReader fr = new FileReader(fileName + ".txt");
fileRead = 1;
BufferedReader br = new BufferedReader(fr);
String str;
int line = 0;
while((str = br.readLine()) != null){
score = input.nextInt();
player = input.next();
System.out.println(str);
line++;
score = score + score;
count++;
}
System.out.println(count);
System.out.println(score);
br.close();
}
catch (Exception ex){
System.out.println("There is no shop named: " + fileName);
}
}
}
The way you used BufferReader with Scanner is totally wrong .
Note: you can use BufferReader in Scanner constructor.
For example :
try( Scanner input = new Scanner( new BufferedReader(new FileReader("your file path goes here")))){
}catch(IOException e){
}
Note: your file reading process or other processes must be in try block because in catch block you cannot do anything because your connection is closed. It is called try catch block with resources.
Note:
A BufferedReader will create a buffer. This should result in faster
reading from the file. Why? Because the buffer gets filled with the
contents of the file. So, you put a bigger chunk of the file in RAM
(if you are dealing with small files, the buffer can contain the whole
file). Now if the Scanner wants to read two bytes, it can read two
bytes from the buffer, instead of having to ask for two bytes to the
hard drive.
Generally speaking, it is much faster to read 10 times 4096 bytes
instead of 4096 times 10 bytes.
Source BufferedReader in Scanner's constructor
Suggestion: you can just read each line of your file by using BufferReader and do your parsing by yourself, or you can use Scanner class that gives you ability to do parsing tokens.
difference between Scanner and BufferReader
As a hint you can use this sample for your parsing goal
Code:
String input = "Kick 20";
String[] inputSplited = input.split(" ");
System.out.println("My splited name is " + inputSplited[0]);
System.out.println("Next year I am " + (Integer.parseInt(inputSplited[1])+1));
Output:
My splited name is Kick
Next year I am 21
Hope you can fixed your program by given hints.
My problem could be solved if Scanner class had previous() method on it. I am asking this question to know if there are any methods to achieve this functionality.
Input:
a file with contents like
a,1
a,2
a,3
b,1
c,1
c,2
c,3
c,4
d,1
d,2
d,3
e,1
f,1
I need to create a list of all lines that has same alphabet.
try {
Scanner scanner = new Scanner(new File(fileName));
List<String> procList = null;
String line =null;
while (scanner.hasNextLine()){
line = scanner.nextLine();
System.out.println(line);
String[] sParts = line.split(",");
procList = new ArrayList<String>();
procList.add(line);
boolean isSamealpha = true;
while(isSamealpha){
String s1 = scanner.nextLine();
if (s1.contains(sParts[0])){
procList.add(s1);
}else{
isSamealpha = false;
System.out.println(procList);
}
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
I get output like
a,1
[a,1, a,2, a,3]
c,1
[c,1, c,2, c,3, c,4]
d,2
[d,2, d,3]
f,1
[f,1]
As you can see it missed list for b and e. If I has scanner.previous() method, I would have put it in else of second while loop. Because there is no previous method, I am stuck.
Please let me know if there are any methods I can use. I can't use FileUtils.readLines() because its a 3GB file and I don't want to use my java memory to store all the file.
I would suggest reconsidering your algorithm instead. You are missing tokens because your algorithm involves reading ahead to determine when the sequence has broken, yet you aren't collecting that next line of input into the same structures that you are placing "duplicate" entries.
You can solve this without needing to read backwards. If you know that the input is always sorted, just read line by line and keep a reference to the last line (to compare with the current one).
Below is some sample code that should help. (I only typed this; I did no checking.)
Scanner scanner = new Scanner(new File(fileName));
List<String> procList = null;
String line = null;
String previousAlpha = null;
while (scanner.hasNextLine()){
line = scanner.nextLine();
if (previousAlpha == null) {
// very first line in the file
procList = new ArrayList<String>();
procList.add(line);
System.out.println(line);
previousAlpha = line.split(",")[0];
}
else if (line.contains(previousAlpha)) {
// same letter as before
procList.add(line);
}
else {
// new letter, but not the very first
// line
System.out.println(procList);
procList = new ArrayList<String>();
procList.add(line);
System.out.println(line);
previousAlpha = line.split(",")[0];
}
}