We Keep Coding

Java issue that doesn't stop the program from running but will return errors

package com.Text.Scanner.java;
import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
public class TextScanner {
public static void main(String ...args) throws IOException{
Scanner sc = new Scanner(System.in);
System.out.println("Enter names for parsing");
String input = sc.nextLine();
ArrayList<String> names = new ArrayList<String>();
for (int i = 0;i<=input.length();i++) {
names.add(input.substring(0, input.indexOf(",")));
input = input.substring(input.indexOf(",")+1);
}
I had issues here but I didn't think much of it, could be this
System.out.println(names);
// handles the string import to arraylist
BufferedReader reader;
try {
reader = new BufferedReader(new FileReader("file location"));
//finds file
String line = reader.readLine();
//reads line
while (line != null) {
for (int i = 0; i <= line.length(); i++) {
if (line.contains(names.get(i))) {
//gets name from array to scan line for
System.out.println(line.substring(4, line.indexOf(names.get(i)) + names.get(i).length()));
//controls length
line = reader.readLine();
}
}
}
reader.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
It returns this:
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index 4 out of bounds for length 4
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
at java.base/java.util.Objects.checkIndex(Objects.java:373)
at java.base/java.util.ArrayList.get(ArrayList.java:426)
at com.Text.Scanner.java.TextScanner.main(TextScanner.java:32)
My goal is to setup a program that will scan the text file for a list of names (first and last) and then return the data associated with them.

The problem was here:
for (int i = 0; i < line.length(); i++) {
if (line.contains(names.get(i))) {
//gets name from array to scan line for
System.out.println(line.substring(4, line.indexOf(names.get(i)) + names.get(i).length()));
//controls length
line = reader.readLine();
}
}
The reason why it didn't work is because the length of line is bigger than the arraylist, the solution is to do this instead:
for (int i = 0; i < names.size(); i++) {
if (line.contains(names.get(i))) {
//gets name from array to scan line for
System.out.println(line.substring(4, line.indexOf(names.get(i)) + names.get(i).length()));
//controls length
line = reader.readLine();
}
}

Sorting .csv Id's in natural order Java

I'm trying to write some code that will take in a list of IDs (numbers and letters) from a .csv file and output them to a new file with the IDs in "natural order". My files are compiling, but I am getting the error:
java.lang.NumberFormatException: For input string: "Alpha"
I think the issue is I am not accounting for both number and letter values in the .csv file. What am I doing wrong?! Sorry if my variable Id's are confusing...
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
public class IdReader {
public static String CSV_FILE_PATH = "/Users/eringray/Desktop/idreader/idData.csv";
public static void main(String[] args){
try {
BufferedReader br = new BufferedReader(new FileReader(CSV_FILE_PATH));
BufferedWriter bw = new BufferedWriter(new FileWriter(CSV_FILE_PATH + ".tsv"));
ArrayList<String> textIds = new ArrayList<>();
ArrayList<Integer> numberIds = new ArrayList<>();
String line = "";
while((line = br.readLine()) != null) {
String[] values = line.split(" ");
if(values.length == 1) {
String idAsString = values[0];
try{
int id = Integer.parseInt(idAsString);
numberIds.add(id);
}
catch(NumberFormatException e){
textIds.add(idAsString);
}
}
}
Collections.sort(textIds);
Collections.sort(numberIds);
for(int i = 0; i < textIds.size(); i++){
String stu = textIds.get(i);
String lineText = stu.toString();
bw.write(lineText);
bw.newLine();
}
for(int i = 0; i < numberIds.size(); i++){
int numValues = numberIds.get(i);
bw.write(numValues);
bw.newLine();
}
br.close();
bw.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

The exception is coming at this line
int id = Integer.parseInt(idAsString);
Clearly alpha is not an integer, so it will throw NumberFormatException. In a case, where you encounter such Strings which cannot be converted into numbers, you can either skips them or throw an exception.
Update
//Use two seperate lists, one for maintaining numbers and other for text
ArrayList<String> textIds = new ArrayList<>();
ArrayList<Integer> numberIds = new ArrayList<>();
String line = "";
while((line = br.readLine()) != null) {
String[] values = line.split(" ");
if(values.length == 1) {
String idAsString = values[0];
try {
//Parse the value. If successful, it means it was a number. Add to integer array.
int id = Integer.parseInt(idAsString);
numberIds.add(id);
}catch (NumberFormatException e){
//If not successful, it means it was a string.
textIds.add(idAsString);
}
}
}
//In the end sort both the list
Collections.sort(textIds);
Collections.synchronizedList(numberIds);
for(int i = 0; i < textIds.size(); i++){
String stu = textIds.get(i);
bw.write(stu);
bw.newLine();
}
for(int i = 0; i < numberIds.size(); i++){
int numValues = numberIds.get(i);
bw.write(numValues+"");
bw.newLine();
}
br.close();
bw.close();
I am not putting code for writing this data to a new file. I hope you can do that.
Sample Input
4
6
33
2
5632
23454
Alpha
So after running my code
numberIds will have [ 2,4,6,33,5632,23454]
textIds will have ["Alpha"]

NumberFormatException occurs because of AlphaNumeric characters in the input.
Please use isNumeric(str) metod in https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html api to verify whether the input is numeric or not and convert to int , only it is numeric

Replace lines in File with another string

I have a text file with the following contents:
public class MyC{
public void MyMethod()
{
System.out.println("My method has been accessed");
System.out.println("hi");
}
}
I have an array num[]= {2,3,4}; which contains the line numbers to be completely replaced with the strings from this array
String[] VALUES = new String[] {"AB","BC","CD"};
That is line 2 will be replaced with AB, line 3 with BD and ine 4 with CD.
Lines which are not in the num[]array have to be written to a new file along with the changes made.
I have this so far.I tried several kind of loops but still it does not work.
public class ReadFileandReplace {
/**
* #param args
*/
public static void main(String[] args) {
try {
int num[] = {3,4,5};
String[] VALUES = new String[] {"AB","BC","CD"};
int l = num.length;
FileInputStream fs= new FileInputStream("C:\\Users\\Antish\\Desktop\\Test_File.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fs));
LineNumberReader reader = new LineNumberReader(br);
FileWriter writer1 = new FileWriter("C:\\Users\\Antish\\Desktop\\Test_File1.txt");
String line;
int count =0;
line = br.readLine();
count++;
while(line!=null){
System.out.println(count+": "+line);
line = br.readLine();
count++;
int i=0;
if(count==num[i]){
int j=0;;
System.out.println(count);
String newtext = line.replace(line, VALUES[j]) + System.lineSeparator();
j++;
writer1.write(newtext);
}
i++;
writer1.append(line);
}
writer1.close();
}
catch (IOException e) {
e.printStackTrace();
} finally {
}
}
}
The expected output should look like this:
public class MyC{
AB
BC
CD
Sys.out.println("hi");
}
}
When I run the code, all lines appear on the same line.

You've done almost, I've updated your code with a map. Check this
int num[] = {3, 4, 5};
String[] values = new String[]{"AB", "BC", "CD"};
HashMap<Integer,String> lineValueMap = new HashMap();
for(int i=0 ;i<num.length ; i++) {
lineValueMap.put(num[i],values[i]);
}
FileInputStream fs = new FileInputStream("test.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fs));
FileWriter writer1 = new FileWriter("test1.txt");
int count = 1;
String line = br.readLine();
while (line != null) {
String replaceValue = lineValueMap.get(count);
if(replaceValue != null) {
writer1.write(replaceValue);
} else {
writer1.write(line);
}
writer1.write(System.getProperty("line.separator"));
line = br.readLine();
count++;
}
writer1.flush();

You're appending each line to the same string. You should add the line separator character at the end of each line as well. (You can do this robustly using System.getProperty("line.separator"))

you have not appended end line character.
writer1.append(line); is appending the data in line without endline character. Thus it is showing in one line. You might need to change it to:
writer1.append(line).append("\n");

Try This
package src;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.TimeZone;
public class MainTest {
static int i ;
public static void main(String[] arg)
{
try {
int num[] = {3,4,5};
String[] VALUES = new String[] {"AB","BC","CD"};
FileInputStream fs= new FileInputStream("C:\\Test\\ren.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fs));
FileWriter writer1 = new FileWriter("C:\\Test\\ren1.txt");
String line;
Integer count =0;
line = br.readLine();
count++;
while(line!=null){
for(int index =0;index<num.length;index++){
if(count == num[index]){
line = VALUES[index];
}
}
writer1.write(line+System.getProperty("line.separator"));
line = br.readLine();
count++;
}
writer1.close();
}
catch (Exception e) {
e.printStackTrace();
} finally {
}
}
}

How to read last 5 lines of a .txt file into java

I have a text file that consists of several entries such as:
hello
there
my
name
is
JoeBloggs
How would I read the last five entries in descending order, i.e. from JoeBloggs - there
I currently have code to read the LAST LINE only:
public class TestLastLineRead {
public static void main(String[] args) throws Exception {
FileInputStream in = new FileInputStream(file.txt);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine = null, tmp;
while ((tmp = br.readLine()) != null) {
strLine = tmp;
}
String lastLine = strLine;
System.out.println(lastLine);
in.close();
}
}

You can add the lines to a List, e.g. a LinkedList. When the list has more than five lines, remove the first/last.
List<String> lines = new LinkedList<String>();
for(String tmp; (tmp = br.readLine()) != null;)
if (lines.add(tmp) && lines.size() > 5)
lines.remove(0);

One very easy way would be to use the CircularFifoBuffer class from the Apache Commons Collections library. It's basically a list of a fixed size that discards old elements when it's full and you add new ones. So you'd create a CircularFifoBuffer of size 5, then add all the lines to it. At the end, it'd contain just the last five lines of the file.

we can use MemoryMappedFile for printing last 5 lines:
private static void printByMemoryMappedFile(File file) throws FileNotFoundException, IOException{
FileInputStream fileInputStream=new FileInputStream(file);
FileChannel channel=fileInputStream.getChannel();
ByteBuffer buffer=channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
buffer.position((int)channel.size());
int count=0;
StringBuilder builder=new StringBuilder();
for(long i=channel.size()-1;i>=0;i--){
char c=(char)buffer.get((int)i);
builder.append(c);
if(c=='\n'){
if(count==5)break;
count++;
builder.reverse();
System.out.println(builder.toString());
builder=null;
builder=new StringBuilder();
}
}
channel.close();
}
RandomAccessFile to print last 5 lines:
private static void printByRandomAcessFile(File file) throws FileNotFoundException, IOException{
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r");
int lines = 0;
StringBuilder builder = new StringBuilder();
long length = file.length();
length--;
randomAccessFile.seek(length);
for(long seek = length; seek >= 0; --seek){
randomAccessFile.seek(seek);
char c = (char)randomAccessFile.read();
builder.append(c);
if(c == '\n'){
builder = builder.reverse();
System.out.println(builder.toString());
lines++;
builder = null;
builder = new StringBuilder();
if (lines == 5){
break;
}
}
}
}

Try this code, a list of length 5 is scanned through all the lines, finally the list is reversed. I edited / modified your code, test it to see it's fully working.
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class Test
{
public static void main(String[] args) throws Exception
{
ArrayList<String> bandWidth = new ArrayList<String>();
FileInputStream in = new FileInputStream("file.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String tmp;
while ((tmp = br.readLine()) != null)
{
bandWidth.add(tmp);
if (bandWidth.size() == 6)
bandWidth.remove(0);
}
ArrayList<String> reversedFive = new ArrayList<String>();
for (int i = bandWidth.size() - 1; i >= 0; i--)
reversedFive.add(bandWidth.get(i));
in.close();
}
}

If all it really does have to do is print last 5 lines:
ArrayList<String> lines = new ArrayList<String>();
String tmp="";
while ((tmp = br.readLine()) != null) {
lines.add(tmp);
}
for (int i = lines.size()-5; i < lines.size(); i++) {
System.out.println(lines.get(i-1));
}

First you have to read the file line by line and add each line to a list. Once the file is read completely, you can print each element in the list in reverse order as shown below:
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
public class FileReader {
public static List<String> readFile() throws IOException {
List<String> fileContents = new ArrayList<String>();
FileInputStream fileInputStream = new FileInputStream("C:/Users/compaq/Desktop/file.txt");
InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String strLine = null;
while((strLine=bufferedReader.readLine())!=null) {
fileContents.add(strLine);
}
fileInputStream.close();
return fileContents;
}
public static void printFileInReverse(List<String> fileContents, int numberOfLines) {
int counter = 0;
for(int i=(fileContents.size()-1);i>=0;i--) {
if(counter==numberOfLines) { break; }
System.out.println(fileContents.get(i));
counter++;
}
}
public static void main(String[] args) throws IOException {
List<String> fileContents = new ArrayList<String>();
fileContents = FileReader.readFile();
int numberOfLines = 5;// Number of lines that you would like to print from the bottom of your text file.
FileReader.printFileInReverse(fileContents, numberOfLines);
}
}

Try this.
This give for last 5 line.
public static void main(String[] args) throws IOException {
List<String > list =new ArrayList<String>();
FileInputStream in = new FileInputStream("C:/adminconsole.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine ="", tmp;
while ((tmp = br.readLine()) != null){
//strLine =tmp+"\n"+strLine;
list.add(tmp);
}
if(list.size()>5){
for (int i=list.size()-1; i>=(list.size()-5); i--) {
System.out.println(list.get(i));
}
}else{
for (int i=0; i<5; i++) {
System.out.println(list.get(i));
}
}
}
}

Follow This Code To Improve Core Java Logic By Using Collectios.
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Scanner;
public class REVERSE {
public static void main(String[] args) {
ArrayList<String> al = new ArrayList<String>();
try {
Scanner sc = new Scanner(new FileReader("input.txt"));
while (sc.hasNextLine()) {
al.add(sc.nextLine());
}
System.out.println(al.get(0));
System.out.println(al.get(1));
System.out.println(al.get(2));
System.out.println(al.get(3));
System.out.println(al.get(4));
Collections.reverse(al);
/*
* for (String s : al) { System.out.println(s); }
*/
System.out.println(al.get(0));
System.out.println(al.get(1));
System.out.println(al.get(2));
System.out.println(al.get(3));
System.out.println(al.get(4));
/*
* for (int i = 0; i < al.size(); i++) {
* System.out.println(al.get(i)); }
*/
} catch (FileNotFoundException e) {
}
}
}

Please try this code. It is working fine for me.
public static void main(String[] args)
{
try
{
int numOfLastline = 10;
BufferedReader reader = new BufferedReader(new FileReader("Text.txt"));
int lines = 0;
while (reader.readLine() != null)
lines++;
reader.close();
System.out.println(lines);
String printedLine = null;
List<String> listForString = new ArrayList<String>();
for (int i = lines - 1; i >= (lines - numOfLastline); i--)
{
printedLine = (String) FileUtils.readLines(new File("Text.txt"), "ISO-8859-1").get(i);
System.out.println(printedLine);
listForString.add(printedLine);
}
System.out.println("\n\n============ Printing in Correct order =============\n\n");
Collections.reverse(listForString);
for (int k = 0; k < listForString.size() ; k++)
{
System.out.println(listForString.get(k));
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
Note : Provide your needed last line numbers at numOfLastline and file [instead of this Text.txt].

Find a specific line of a text file (not by line_number) and store it as a new String

I am trying to read a text file in java using FileReader and BufferedReader classes. Following an online tutorial I made two classes, one called ReadFile and one FileData.
Then I tried to extract a small part of the text file (i.e. between lines "ENTITIES" and "ENDSEC"). Finally l would like to tell the program to find a specific line between the above-mentioned and store it as an Xvalue, which I could use later.
I am really struggling to figure out how to do the last part...any help would be very much apprciated!
//FileData Class
package textfiles;
import java.io.IOException;
public class FileData {
public static void main (String[] args) throws IOException {
String file_name = "C:/Point.txt";
try {
ReadFile file = new ReadFile (file_name);
String[] aryLines = file.OpenFile();
int i;
for ( i=0; i < aryLines.length; i++ ) {
System.out.println( aryLines[ i ] ) ;
}
}
catch (IOException e) {
System.out.println(e.getMessage() );
}
}
}
// ReadFile Class
package textfiles;
import java.io.IOException;
import java.io.FileReader;
import java.io.BufferedReader;
import java.lang.String;
public class ReadFile {
private String path;
public ReadFile (String file_path) {
path = file_path;
}
public String[] OpenFile() throws IOException {
FileReader fr = new FileReader (path);
BufferedReader textReader = new BufferedReader (fr);
int numberOfLines = readLines();
String[] textData = new String[numberOfLines];
String nextline = "";
int i;
// String Xvalue;
for (i=0; i < numberOfLines; i++) {
String oneline = textReader.readLine();
int j = 0;
if (oneline.equals("ENTITIES")) {
nextline = oneline;
System.out.println(oneline);
while (!nextline.equals("ENDSEC")) {
nextline = textReader.readLine();
textData[j] = nextline;
// xvalue = ..........
j = j + 1;
i = i+1;
}
}
//textData[i] = textReader.readLine();
}
textReader.close( );
return textData;
}
int readLines() throws IOException {
FileReader file_to_read = new FileReader (path);
BufferedReader bf = new BufferedReader (file_to_read);
String aLine;
int numberOfLines = 0;
while (( aLine = bf.readLine()) != null ) {
numberOfLines ++;
}
bf.close ();
return numberOfLines;
}
}

I don't know what line you are specifically looking for but here are a few methods you might want to use to do such operation:
private static String START_LINE = "ENTITIES";
private static String END_LINE = "ENDSEC";
public static List<String> getSpecificLines(Srting filename) throws IOException{
List<String> specificLines = new LinkedList<String>();
Scanner sc = null;
try {
boolean foundStartLine = false;
boolean foundEndLine = false;
sc = new Scanner(new BufferedReader(new FileReader(filename)));
while (!foundEndLine && sc.hasNext()) {
String line = sc.nextLine();
foundStartLine = foundStartLine || line.equals(START_LINE);
foundEndLine = foundEndLine || line.equals(END_LINE);
if(foundStartLine && !foundEndLine){
specificLines.add(line);
}
}
} finally {
if (sc != null) {
sc.close();
}
}
return specificLines;
}
public static String getSpecificLine(List<String> specificLines){
for(String line : specificLines){
if(isSpecific(line)){
return line;
}
}
return null;
}
public static boolean isSpecific(String line){
// What makes the String special??
}

When I get it right you want to store every line between ENTITIES and ENDSEC?
If yes you could simply define a StringBuffer and append everything which is in between these to keywords.
// This could you would put outside the while loop
StringBuffer xValues = new StringBuffer();
// This would be in the while loop and you append all the lines in the buffer
xValues.append(nextline);
If you want to store more specific data in between these to keywords then you probably need to work with Regular Expressions and get out the data you need and put it into a designed DataStructure (A class you've defined by our own).
And btw. I think you could read the file much easier with the following code:
BufferedReader reader = new BufferedReader(new
InputStreamReader(this.getClass().getResourceAsStream(filename)));
try {
while ((line = reader.readLine()) != null) {
if(line.equals("ENTITIES") {
...
}
} (IOException e) {
System.out.println("IO Exception. Couldn't Read the file!");
}
Then you don't have to read first how many lines the file has. You just start reading till the end :).
EDIT:
I still don't know if I understand that right. So if ENTITIES POINT 10 1333.888 20 333.5555 ENDSEC is one line then you could work with the split(" ") Method.
Let me explain with an example:
String line = "";
String[] parts = line.split(" ");
float xValue = parts[2]; // would store 10
float yValue = parts[3]; // would store 1333.888
float zValue = parts[4]; // would store 20
float ... = parts[5]; // would store 333.5555
EDIT2:
Or is every point (x, y, ..) on another line?!
So the file content is like that:
ENTITIES POINT
10
1333.888 // <-- you want this one as xValue
20
333.5555 // <-- and this one as yvalue?
ENDSEC
BufferedReader reader = new BufferedReader(new
InputStreamReader(this.getClass().getResourceAsStream(filename)));
try {
while ((line = reader.readLine()) != null) {
if(line.equals("ENTITIES") {
// read next line
line = reader.readLine();
if(line.equals("10") {
// read next line to get the value
line = reader.readLine(); // read next line to get the value
float xValue = Float.parseFloat(line);
}
line = reader.readLine();
if(line.equals("20") {
// read next line to get the value
line = reader.readLine();
float yValue = Float.parseFloaT(line);
}
}
} (IOException e) {
System.out.println("IO Exception. Couldn't Read the file!");
}
If you have several ENTITIES in the file you need to create a class which stores the xValue, yValue or you could use the Point class. Then you would create an ArrayList of these Points and just append them..