Develop Reference

Java ArrayIndexOutOfBoundsException keeps appearing while trying to find most occuring word in file

I am currently building a program which reads a file and prints the most occurring words and how many times each word appears like so:
package WordLookUp;
import java.util.*;
import java.io.*;
import java.lang.*;
public class WordLookUp {
private String[] mostWords;
private Scanner reader;
private String line;
private FileReader fr;
private BufferedReader br;
private List<String> original;
private String token = " ";
public WordLookUp(String file) throws Exception {
this.reader = new Scanner(new File(file));
this.original = new ArrayList<String>();
while (this.reader.hasNext()) { //reads file and stores it in string
this.token = this.reader.next();
this.original.add(token); //adds it to my arrayList
}
}
public void findMostOccurringWords() {
List<String> mostOccur = new ArrayList<String>();
List<Integer> count = new ArrayList<Integer>();
int counter = 0;
this.mostWords = this.token.split(" "); //storing read lines in mostWords arrayList
try {
for (int i = 0; i < original.size(); i++) {
if (this.original.equals(this.mostWords[i])) {
counter++; //increase counter
mostOccur.add(this.mostWords[i]);
count.add(counter);
}
}
for (int i = 0; i < mostOccur.size(); i++) {
System.out.println("Word: " + mostOccur.get(i) + " count: " + count.get(i));
}
} catch (ArrayIndexOutOfBoundsException ae) {
System.out.println("Illegal index");
}
}
}
package WordLookUp;
import java.util.*;
import java.io.*;
public class Main {
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
WordLookUp wL = new WordLookUp("tiny1.txt");
wL.findMostOccurringWords();
}
}
So when I keep running my file, it throws the exception I gave it: "Illegal index". I think it is my findMostOccuringWords method. To me the logic feels correct, but I don't know why it is throwing an ArrayIndexOutOfBoundsException. I tried playing with the for loops and tried to go from int i = 0 to i < mostOccur.size() - 1 but that is not working either. Is my logic wrong ? I am not allowed to use a hashmap and our professor gave us a hint that we can do this assignment easily with arrays and ArrayLists (no other built in functions, but regexes is highly recommended for use as well for the rest of the assignment). I put a private FileReader and BufferedReader up there as I am trying to see if they would work better or not. Thanks for the advice!

Can you try to use the following codes? I think your current algorithm is wrong.
public class WordLookUp {
private List<String> original;
private List<String> mostOccur = new ArrayList<String>();
private List<Integer> count = new ArrayList<Integer>();
public WordLookUp(String file) throws Exception {
try(Scanner reader = new Scanner(new File(file));){
this.original = new ArrayList<String>();
String token = " ";
while (reader.hasNext()) { //reads file and stores it in string
token = reader.next();
this.original.add(token); //adds it to my arrayList
findMostOccurringWords(token);
}
}
}
public void findMostOccurringWords(String token) {
int counter = 0;
String[] mostWords = token.split(" "); //storing read lines in mostWords arrayList
try {
for (int i = 0; i < mostWords.length; i++) {
for(int j = 0; j < this.original.size(); j++) {
if (original.get(j).equals(mostWords[i])) {
counter++; //increase counter
}
}
if (mostOccur.contains(mostWords[i])) {
count.set(mostOccur.indexOf(mostWords[i]),counter);
}else {
mostOccur.add(mostWords[i]);
count.add(counter);
}
}
} catch (ArrayIndexOutOfBoundsException ae) {
System.out.println("Illegal index");
}
}
public void count() {
for (int i = 0; i < mostOccur.size(); i++) {
System.out.println("Word: " + mostOccur.get(i) + " count: " + count.get(i));
}
}
}
public class Main {
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
WordLookUp wL = new WordLookUp("F:\\gc.log");
wL.count();
}
}

Here in this loop:
for (int i = 0; i < mostOccur.size(); i++) {
System.out.println("Word: " + mostOccur.get(i) + " count: " + count.get(i));
}
You check to make sure that i is within bounds for mostOccur but not count. I would add a condition to check to make sure it is in bounds. Such as:
for (int i = 0; i < mostOccur.size() && i < count.size(); i++) {
System.out.println("Word: " + mostOccur.get(i) + " count: " + count.get(i));
}

Exception when trying to instrument source code by WALA: java.lang.ClassFormatError: StackMapTable format error: wrong attribute size

I have a simple program like this:
package tests;
import java.util.Scanner;
public class TestSum {
public static void main(String[] args) {
int sum = 0;
System.out.print("Please enter starting i: ");
int i = new Scanner(System.in).nextInt();
while ( i < 11 ) {
sum = sum + i;
i = i + 1;
}
System.out.println("sum = " + sum);
System.out.println("Ending i = " + i);
}
}
I built this into a jar file and I want to use WALA to add more instrumented source code to count the number of loop execution for dynamic analysis purpose.
This is what I have done by using Wala, most of the stuffs is taken from this example Wala Bench Example
import com.ibm.wala.shrikeBT.*;
import com.ibm.wala.shrikeBT.analysis.Verifier;
import com.ibm.wala.shrikeBT.shrikeCT.CTDecoder;
import com.ibm.wala.shrikeBT.shrikeCT.ClassInstrumenter;
import com.ibm.wala.shrikeBT.shrikeCT.OfflineInstrumenter;
import com.ibm.wala.shrikeCT.ClassWriter;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.PrintStream;
import java.io.Writer;
/**
* Created by quocnghi on 2/2/17.
*/
public class InstrumentedTest {
private final static boolean disasm = true;
private final static boolean verify = true;
private static OfflineInstrumenter instrumenter = new OfflineInstrumenter(true);
public static void main(String[] args) throws Exception {
for (int i = 0; i < 1; i++) {
Writer w = new BufferedWriter(new FileWriter("report", false));
args = instrumenter.parseStandardArgs(args);
instrumenter.setPassUnmodifiedClasses(true);
instrumenter.beginTraversal();
ClassInstrumenter ci;
while ((ci = instrumenter.nextClass()) != null) {
doClass(ci, w);
}
instrumenter.close();
}
}
static final String fieldName = "_Bench_enable_trace";
// Keep these commonly used instructions around
static final Instruction getSysOut = Util.makeGet(System.class, "out");
static final Instruction callPrintln = Util.makeInvoke(PrintStream.class, "println", new Class[]{String.class});
private static void doClass(final ClassInstrumenter ci, Writer w) throws Exception {
final String className = ci.getReader().getName();
System.out.println("Class name : " + className);
w.write("Class: " + className + "\n");
w.flush();
for (int m = 0; m < ci.getReader().getMethodCount(); m++) {
MethodData d = ci.visitMethod(m);
System.out.println(d.getName());
// d could be null, e.g., if the method is abstract or native
if (d != null) {
w.write("Instrumenting " + ci.getReader().getMethodName(m) + " " + ci.getReader().getMethodType(m) + ":\n");
w.flush();
if (disasm) {
w.write("Initial ShrikeBT code:\n");
(new Disassembler(d)).disassembleTo(w);
w.flush();
}
if (verify) {
Verifier v = new Verifier(d);
v.verify();
}
MethodEditor methodEditor = new MethodEditor(d);
methodEditor.beginPass();
final int noTraceLabel = methodEditor.allocateLabel();
IInstruction[] instr = methodEditor.getInstructions();
final String msg0 = "Loop called at " + Util.makeClass("L" + ci.getReader().getName() + ";") + "."
+ ci.getReader().getMethodName(m);
int i = 0;
for (IInstruction in : instr) {
if (in instanceof ConditionalBranchInstruction) {
int b = i;
methodEditor.insertBefore(i, new MethodEditor.Patch() {
#Override
public void emitTo(MethodEditor.Output w) {
w.emit(getSysOut);
w.emit(ConstantInstruction.makeString(msg0));
w.emit(callPrintln);
w.emitLabel(noTraceLabel);
}
});
}
i++;
System.out.println(in.toString());
}
methodEditor.applyPatches();
if (disasm) {
w.write("Final ShrikeBT code:\n");
(new Disassembler(d)).disassembleTo(w);
w.flush();
}
}
}
ClassWriter cw = ci.emitClass();
instrumenter.outputModifiedClass(ci, cw);
}
}
I expect that after adding more instrumented code, the program should become like this, which add a line System.out.println in the loop :
package tests;
import java.util.Scanner;
public class TestSum {
public static void main(String[] args) {
int sum = 0;
System.out.print("Please enter starting i: ");
int i = new Scanner(System.in).nextInt();
while ( i < 11 ) {
sum = sum + i;
i = i + 1;
System.out.println("One count for this loop");
}
System.out.println("sum = " + sum);
System.out.println("Ending i = " + i);
}
}
But I got this error :
java.lang.ClassFormatError: StackMapTable format error: wrong attribute size

WALA does have StackMapTable support, but perhaps something is broken. I suggest filing an issue.

Make this program more efficient?

just curious if anyone has any idea for making this program more simple. It reads records from a database into an ArrayList and allows the user to search for records by state. It processes a database of 1 million records in aprox 16000ms.
import java.sql.*;
import java.util.*;
public class ShowEmployeeDB
{
public static void main(String args[])
{
ArrayList <String> Recs = new ArrayList <String>();
String driverName = "sun.jdbc.odbc.JdbcOdbcDriver";
String connectionURL = "jdbc:odbc:CitizensDB";
Connection con = null;
Statement stmt = null;
String sqlStatement = "SELECT * FROM Citizens";
ResultSet rs = null;
int r = 0;
Scanner scan = new Scanner(System.in);
String search = null;
long starttime = System.currentTimeMillis();
try
{
Class.forName(driverName).newInstance();
con = DriverManager.getConnection(connectionURL);
stmt = con.createStatement();
rs = stmt.executeQuery(sqlStatement);
String ID = null;
String Age = null;
String State = null;
String Gender = null;
String Status = null;
String record = null;
while (rs.next())
{
for (int k = 1; k <= 1; ++k)
{
ID = rs.getString(k) + " ";
for (int j = 2; j <= 2; ++j)
Age = rs.getString(j) + " ";
for (int i = 3; i <= 3; ++i)
State = rs.getString(i).toUpperCase() + " ";
for (int h = 4; h <= 4; ++h)
Gender = rs.getString(h) + " ";
for (int g = 5; g <= 5; ++g)
Status = rs.getString(g) + " ";
}//for
record = ID + Age + State + Gender + Status;
Recs.add(record);
++r;
}//while
rs.close();
stmt.close();
con.close();
} catch (Exception ex) { ex.printStackTrace(); }
String endtime = System.currentTimeMillis() - starttime + "ms";
System.out.println(endtime);
System.out.print("Enter A Search State: ");
search = scan.nextLine().toUpperCase();
Iterator<String> iter = Recs.iterator();
while(iter.hasNext())
{
String s = iter.next();
if (s.contains(search))
{
System.out.println(s);
}
}//while
} // main
} // ShowEmployeeBD
Any advice would be greatly appreciated. Thank you in advance!

If search is not often, I would suggest to take the search string input before running the query, so that search results are directly from the DB. I this case you do not have to reiterate all 1 million records.

Perform searching directly on DB rather than fetching all the records and searching through java code.
Also if search is on multiple column, then prepare a meta data in DB at a single place on the basis of IDs, and the meta data can further be used for fetching the required results that match the query.

Separate your logic from the technical stuff. In such a convolut it is difficult to run unit tests or any optimizations.
Why do you need for loops, when only asking one value.
Use StringBuilder instead of String concatenation.
Use either try-with or put your close statements in a finally clause.
Don't initialize variables you don't need (r).
Use for each statements.
Query the database, not the result set.
Tune your database.
If you are only searching for a state, filter only those, so build an object and compare the state instead of a string contains.
Compare the state before storing strings in the list.
Tune your list because it constantly grows with 1Mio records.
Use a hashset instead of an arraylist.
Develop against interfaces.
A better program might look like following:
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
public class ShowEmployeeDB {
private static final String DRIVERNAME = "sun.jdbc.odbc.JdbcOdbcDriver";
private static final String CONNECTIONURL = "jdbc:odbc:CitizensDB";
private static final String SELECT_CITIZENS = "SELECT * FROM Citizens";
static {
try {
DriverManager.registerDriver((Driver) Class.forName(DRIVERNAME).newInstance());
} catch (InstantiationException | IllegalAccessException | ClassNotFoundException | SQLException e) {
e.printStackTrace();
}
}
public static void main(final String args[]) {
System.out.print("Enter A Search State: ");
searchRecords();
}
private static void searchRecords() {
try(Scanner scan = new Scanner(System.in);) {
final String state = scan.nextLine();
final long starttime = System.currentTimeMillis();
final Set<Record> records = searchRecordsByState(state);
System.out.println(System.currentTimeMillis() - starttime + "ms");
for(final Record r : records) {
System.out.println(r);
}
} catch (Exception e) {
e.printStackTrace();
}
}
private static Set<Record> searchRecordsByState(final String stateToFilter) {
final Set<Record> records = new HashSet<>();
try(Connection con = DriverManager.getConnection(CONNECTIONURL);
PreparedStatement stmt = con.prepareStatement(SELECT_CITIZENS);
ResultSet rs = stmt.executeQuery(); ) {
while(rs.next()) {
final String state = rs.getString(3);
if(state.equalsIgnoreCase(stateToFilter)) {
final Record r = new Record(rs.getString(1), rs.getString(2), state, rs.getString(4), rs.getString(5));
records.add(r);
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
return records;
}
}
class Record {
String id, age, state, gender, status;
public Record(String id, String age, String state, String gender, String status) {
this.id = id;
this.age = age;
this.state = state;
this.gender = gender;
this.status = status;
}
public String getState() {
return state;
}
#Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append(id).append(' ')
.append(age).append(' ')
.append(state).append(' ')
.append(gender).append(' ')
.append(status);
return sb.toString();
}
}
This is untested, because I don't have a database with a million entries by hand.
But the best would be to query the database and catch only those entries you need. So use the WHERE-clause in your statement.

How to generate random code and check whether it exist in database or not

I try to generate random code name as licenseKey and check whether it is exist in database or not. If not exist, then display in my jsp page, if exist, continue generating the random code. I got the error "java.lang.StackOverflowError". How to solve this? Below is my code :
package com.raydar.hospital;
import com.raydar.hospital.DB_Connection;
import java.sql.*;
public class RandomCodeGenerator {
String licenseKey = "";
int noOfCAPSAlpha = 4;
int noOfDigits = 4;
int minLen = 8;
int maxLen = 8;
char[] code = RandomCode.generateCode(minLen, maxLen, noOfCAPSAlpha, noOfDigits);
public RandomCodeGenerator(){
}
public String getOutputCode() throws Exception{
String result ="";
result = isLicenseKeyExist();
System.out.println("4 + " +result);
if (result=="false"){
System.out.println("1 + " +new String(code));
licenseKey = new String(code);
}
else if (result=="true"){
System.out.println("2 + " +new String(code));
licenseKey = new String(code);
isLicenseKeyExist ();
}
return licenseKey;
}
private String isLicenseKeyExist () throws Exception{
String code = "";
code = getOutputCode();
Connection connection = null;
Statement statement = null;
ResultSet rs = null;
String result="";
System.out.println("3 + " +code);
try{
DB_Connection connect = new DB_Connection();
connection = connect.getDBConnection();
statement = connection.createStatement();
rs = statement.executeQuery("SELECT licenseKey FROM hospital WHERE licenseKey = '" +code+ "'");
if (rs.next()){
result = "true";
}
else{
result = "false";
}
}catch (Exception e){
System.out.println("Error retrieving data! "+e);
}
return result;
}
}

You create a recursive loop where isLicenseKeyExist() calls getOutputCode(), but then getOutputCode() calls isLicenseKeyExist(). So eventually you run out of stack space, and get this exception.
Here,
public String getOutputCode() throws Exception{
String result ="";
result = isLicenseKeyExist();
...
}
private String isLicenseKeyExist () throws Exception{
String code = "";
code = getOutputCode();
...
}

I think you want something like this. Remove the field called code from your class, and its initialiser, and put the call to RandomCode.generateCode inside your getOutputCode method like this. The reason is that you'll have to call it repeatedly if your code is already in the database.
public String getOutputCode() throws SQLException {
String code;
do {
code = new String(RandomCode.generateCode(minLen, maxLen, noOfCAPSAlpha, noOfDigits));
}
while(licenceKeyExists(code));
return code;
}
private boolean licenceKeyExists(String code) throws SQLException {
try{
DB_Connection connect = new DB_Connection();
connection = connect.getDBConnection();
statement = connection.createStatement();
rs = statement.executeQuery("SELECT licenseKey FROM hospital WHERE licenseKey = '" +code+ "'");
return rs.next();
}
finally {
try {
connection.close();
} catch (SQLException ignored){}
}
}

#aween - #captureSteve has answered the first part of the question .
So, straight to "I wan't to call this function" comment. See, if I
understand your question correctly, you want to generate a key, and
check if it is available in the DB using isLicenseKeyExist() . In such
case, why don't you create the key first, then pass it to the
isLicenseKeyExist(). Then this function will return true/false based
on which you can decide what to do.

connect client side java program to access database

I am making a practice program using java and an access database.
the program is an ultimate tictactoe board and the databse is meant for keeping track of the names of the players and their scores.
the trouble i am having is that i keep getting these errors.
Exception in thread "main" java.lang.NullPointerException
at AccessDatabaseConnection.getName(AccessDatabaseConnection.java:39)
at ultimate.<init>(ultimate.java:39)
at ultimate.main(ultimate.java:82)
with further research i also found this:
[Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
here is my code. the math is a little unfinished in the sql statements but im not really worried about that yet. i need to get this connection between the program and the database.
here is the area of code in my constructor for the program that connects to the accessdatabaseconnections class:
AccessDatabaseConnection DB = new AccessDatabaseConnection();
Font f = new Font("Dialog", Font.BOLD, 80);
public ultimate() {
super("Testing Buttons");
String dbname = DB.getName();
String wins = DB.getWins();
String losses = DB.getLosses();
Container container = getContentPane();
container.setLayout(null);
ButtonHandler handler = new ButtonHandler();
for (int j = 0; j < 9; j++) {// set the rows
x = 10;
for (int i = 0; i < 9; i++) {// set the columns
button[j][i] = new JButton();
container.add(button[j][i]);
button[j][i].setName(Integer.toString(j) + "_"
+ Integer.toString(i));
button[j][i].addActionListener(handler);
button[j][i].setSize(100, 100);
button[j][i].setVisible(true);
button[j][i].setFont(f);
button[j][i].setText(null);
if ((i > 2 && j < 3 && i < 6) || (j > 2 && j < 6 && i < 3)
|| (j > 2 && j < 6 && i < 9 && i > 5)
|| (j > 5 && j < 9 && i < 6 && i > 2)) {
button[j][i].setBackground(Color.LIGHT_GRAY);
} else {
button[j][i].setBackground(Color.WHITE);
}
button[j][i].setLocation(x, y);
x = x + 110;
}
y = y + 110;
}
setSize(1024, 1050);
setVisible(true);
container.setBackground(Color.BLACK);
}
public static void main(String args[]) {
ultimate application = new ultimate();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
PlayerOne = JOptionPane.showInputDialog("Player 1: Enter Your Name");
PlayerTwo = JOptionPane.showInputDialog("Player 2: Enter Your Name");
while(PlayerOne == PlayerTwo){
PlayerTwo = JOptionPane.showInputDialog("Player 2: Re-Enter Your Name (Cannot be the same!)");
}
}
and here is the code for accessing the database:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.logging.Level;
import java.util.logging.Logger;
public class AccessDatabaseConnection {
public static Connection connect() {
Connection con;
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String database ="jdbc:odbc:Driver{Microsoft Access Driver (*.accdb)};DBQ=C:\\Users\\McKenzieC\\Documents\\tictactoeRecords.accdb;";
con = DriverManager.getConnection(database, "", "");
} catch (Exception ex) {
return null;
}
return con;
}
public void addData(String nameOne, int win, String nameTwo,int loss){
try {
Statement stmt = connect().createStatement();
stmt.executeQuery("INSERT INTO t_Records (Name, Wins) " +
"VALUES (" + nameOne + ", " + Integer.toString(win));
/*stmt.executeQuery("INSERT INTO t_Records (Name, Wins) " +
"VALUES (" + nameTwo + ", " + Integer.toString(loss));
+ ", " + Integer.toString(loss)*/
}
catch (SQLException ex) {
}
}
public String getName() {
try {
Statement stmt = connect().createStatement();
ResultSet rset = stmt.executeQuery("SELECT * FROM t_Records");
if (rset.next()) {
String name = rset.getString("Name");
return name;
}
} catch (SQLException ex) {
}
return null;
}
public String getWins() {
try {
Statement stmt = connect().createStatement();
ResultSet rset = stmt.executeQuery("SELECT * FROM t_Records");
if (rset.next()) {
String wins = rset.getString("Wins");
return wins;
}
} catch (SQLException ex) {
}
return null;
}
public String getLosses() {
try {
Statement stmt = connect().createStatement();
ResultSet rset = stmt.executeQuery("SELECT * FROM t_Records");
if (rset.next()) {
String losses = rset.getString("Losses");
return losses;
}
} catch (SQLException ex) {
}
return null;
}
public static void main(String[] args) {
}
}

I assume that you can't see the real error because you're hiding the real error:
Never do this:
catch (Exception ex) {
return null;
}
You can change for this at least (again not recommended but better than the above code):
catch (Exception ex) {
ex.printStackTrace();
return null;
}
//After this change the program will fail again but you will got a better error message
But you always must manage the Exception:
Print a error message
Put a log message (java logging, log4j and so on)
Deal with the error
Re-throw the exception
And son on

The statement...
String database ="jdbc:odbc:Driver{Microsoft Access Driver (*.accdb)};DBQ=C:\\Users\\McKenzieC\\Documents\\tictactoeRecords.accdb;";
...has two problems:
You are missing the equal sign (=) after the Driver keyword.
There is no ODBC driver named Microsoft Access Driver (*.accdb).
Try this instead:
String database ="jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=C:\\Users\\McKenzieC\\Documents\\tictactoeRecords.accdb;";

Is Statement stmt equal null after connect().createStatement();? If yes, then stmt.executeQuery will cause null ptr exception.