Error when trying to read integer with JCreator

Question

*********CODE:
import corejava.*;
class Reverse {
     public static void main(String[] args) {
          int number;
          number = Console.readint("Please enter an integer: ");
***********ERROR:
--------------------Configuration: TEST - j2sdk1.4.2_15 <Default> - <Default>--------------------
C:\Documents and Settings\mik\My Documents\JCreator Pro\MyProjects\a\TEST\src\TEST.java:6: cannot access corejava.Console
bad class file: C:\j2sdk1.4.2_15\jre\lib\ext\corejava.jar(corejava/Console.class)
class file has wrong version 49.0, should be 48.0
Please remove or make sure it appears in the correct subdirectory of the classpath.
number = Console.readint("Please enter an integer: ");
^
1 error
Process completed.
Why is this happening ?
i just cant seem to read an integer from the user no matter what i try :-(
Edited by: miki85 on Oct 1, 2007 5:37 AM

Answer 1

Here's one I used to use back in the 1.5 days... I take no credit for the code though.
package krc.io;
* Keyboard - static methods for basic line-buffered keyboard input.
* Author: J. M. Morris (jmm at dcs gla ac uk).
* Version 1.1 J. M. Morris October 28th 1998.
* Version 1.2 K. R. Corlett January 27th 2007.
* Example of use
* The statements:
*     i=Keyboard.readInt();
*     b=Keyboard.readBoolean();
*     c=Keyboard.readChar();
*     t=Keyboard.readToken();
*     s=Keyboard.readString();
*     System.out.println("> i='"+i+"', b='"+b+"', c='"+c+"', t='"+t+"', and s='"+s+"'");
* Given the Keyboard input:
*     "      23    TRue X   Java123   the  rest   "
* Produce the output:
*     > i=23, b=true, c='X', t="Java123", and s="  the  rest   "
* See: the unit tests in the main method for lots more usage examples.
import java.io.*;
import java.util.List;
import java.util.ArrayList;
public abstract class Keyboard {
    static BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
    static String bfr = "";
    static int bfrlen = 0;
    static int p = 1; // bfr[p..] contains next input
    // BASIC METHODS - READ THE NEXT WORD AND CONVERT IT TO DESIRED TYPE
    // Consume and return the remainder of current line (end-of-line discarded).
    public static String readString() {
        try {
            if( bfr!=null && p>bfrlen ) readLine();
            eofCheck();
            int t=p; p=bfrlen+1;
            return(bfr.substring(t));
        } catch (IOException ex) {
            System.err.println(ex);
            return "";
    public static String readString(String prompt) {
        print(prompt + " (String) : ");
        return readString();
    // Consume and return a character (which may be an end-of-line).
    public static char readChar() {
        try {
            if( bfr!=null && p>bfrlen ) readLine();
            eofCheck();
            char c = (p==bfrlen ? '\n' : bfr.charAt(p-1));
            p++;
            return(c);
        } catch (StringIndexOutOfBoundsException ex) {
            //just silently swallow the exception !!!
            return((char)0);
        } catch (IOException ex) {
            System.err.println(ex);
            return((char)0);
    public static char readChar(String prompt) {
        print(prompt +" (char) : ");
        return readChar();
    // Consume and return a boolean. Trailing delimiter consumed.
    // Any string other than "true" (case insensitive) is false.
    public static boolean readBoolean() {
        try {
            return new Boolean(getToken()).booleanValue();
        } catch (Exception ex) {
            System.err.println(ex);
            return false;
    public static boolean readBoolean(String prompt) {
        print(prompt + " (boolean) : ");
        return readBoolean();
    // Consume and return an integer. Trailing delimiter consumed.
    public static int readInt() {
        try {
            return Integer.parseInt(getToken());
        } catch (Exception ex) {
            System.err.println(ex);
            return 0;
    public static int readInt(String prompt) {
        print(prompt + " (int) : ");
        return readInt();
    // Consume and return a double. Trailing delimiter consumed.
    public static double readDouble() {
        try {
            return new Double(getToken()).doubleValue();
        } catch (Exception ex) {
            System.err.println(ex);
            return 0.0;
    public static double readDouble(String prompt) {
        print(prompt + " (double) : ");
        return readDouble();
    // ADVANCED PUBLIC METHODS
    // Consume and return the next token (word) from input.
    // The trailing delimiter is also consumed. A token is a maximal sequence
    // of non-whitespace characters.
    public static String readToken() {
        try {
            return getToken();
        } catch (IOException ex) {
            System.err.println(ex);
            return "";
    // The next available character if any (which may be an end-of-line). The
    // character is not consumed. If bfr is empty return null character.
    public static char peekChar() {
        if (bfr==null || p>bfrlen) return('\000');
        else if (p==bfrlen) return('\n');
        else return bfr.charAt(p);
    public static int available() {
    // Number of characters available on this line (including end-of-line,
    // which counts as one character, ie '\n')
        if (bfr==null) return 0;
        else return (bfrlen+1-p);
    public static boolean hasMoreTokens() {
    // Are there more tokens on the current line?
        if(bfr==null) return false;
        int q;
        for(q=p; q<bfrlen && isWhitespace(q); q++);
        return(q<bfrlen);
    public static void skipLine() {
    // Skip any remaining input on this line.
        if(bfr!=null) p = bfrlen+1;
    public static void skipWhitespace() {
    // Consumes whitespaces until a non-whitespace character is entered (which
    // is not consumed).
        try {
            skipWhitespaces();
        } catch (IOException ex) {
            System.err.println(ex);
    public static boolean eof() { // NOT More characters?
    // This method is intended for use when stdin has been redirected from file
        if(available()>0) return false;
        try {
            readLine();
        } catch (IOException ex) {
            System.err.println(ex);
        return (bfr == null);
    public static String pause() {
        print("Press return to continue.");
        return(Keyboard.readString());
    public static boolean isWhitespace(int offset) {
        return (Character.isWhitespace(bfr.charAt(offset)));
    // PRIVATE HELPER METHODS
    private static void readLine() throws IOException {
        p = 0;
        bfrlen = 0;
        bfr = null;
        bfr = stdin.readLine();
        bfrlen = bfr.length();
    private static String getToken() throws IOException {
    // Consumes and returns the next word from input.
        skipWhitespaces();
        int t = p++;
        while( p<bfrlen && !(isWhitespace(p)) ) p++;
        return(bfr.substring(t,p++));
    private static void skipWhitespaces() throws IOException {
    // Consumes input until a non-whitespace character is entered (which
    // is not consumed).
        while ( bfr!=null && (p>=bfrlen||isWhitespace(p)) ) {
            if (p>=bfrlen) {
                readLine();
            } else {
                p++;
    private static void eofCheck() throws IOException {
        if(bfr==null) throw new IOException("Unexpected end of file.");
    private static void print(String msg) {
        System.out.print(msg);
    private static void println(String msg) {
        System.out.println(msg);
    // test harness
    public static void main(String[] args) {
        int i;
        double d;
        char c;
        boolean b;
        String s, t, u;
        println("TEST KEYBOARD VERSION 1.1");
        println("-------------------------");
        print("\nEnter a sequence of integers, terminated by -9: ");
        do {
            i = Keyboard.readInt();
            println("> i=^"+i+"^");
        } while(i!=-9);
        print("\nEnter integer character double boolean string: ");
        i = Keyboard.readInt(); println(""+i);
        c = Keyboard.readChar(); println(""+c);
        d = Keyboard.readDouble(); println(""+d);
        b = Keyboard.readBoolean(); println(""+b);
        s = Keyboard.readString(); println(s);
        pause();
        // Test for the empty string
        print("\nTest no input: ");
        s = pause();
        println("> expect s=^^; s=^"+s+"^");
        // Test readInt eats trailing spaces
        println("\nTest readInt eats trailing spaces: Copy & paste the below line:");
        println("3 ");
        i = Keyboard.readInt();
        s = Keyboard.readString();
        println("> expect s=^^; s=^"+s+"^");
        // Test skipWhitespace
        println("\nTest skipWhitespace: Copy & paste the below line");
        println("      123");
        Keyboard.skipWhitespace();
        c = Keyboard.peekChar();
        println("The first non-whitespace you entered was: "+c);
        println("There should be 3 characters available is: "+Keyboard.available());
        Keyboard.skipLine();
        c = Keyboard.peekChar();
        if (c == '\000') println("Nothing available.");
        else println("Available c=^"+c+"^");
        // Test read methods
        println("\nTest read methods: Copy & paste the below line");
        println("      23    TRue X   Java123   the  rest   ");
        i = Keyboard.readInt(); println("> i=^"+i+"^");
        b = Keyboard.readBoolean();  println("> b=^"+b+"^");
        c = Keyboard.readChar(); println("> c=^"+c+"^");
        t = Keyboard.readToken();  println("> t=^"+t+"^");
        s = Keyboard.readString(); println("> s=^"+s+"^");
        // Test hasMoreTokens()
        println("\nTest hasMoreTokens: Enter several words on a line : ");
        List<String> list = new ArrayList<String>(10);
        do {
            list.add(Keyboard.readToken());
        } while(Keyboard.hasMoreTokens());
        Keyboard.skipLine();
        for (String item : list) {
            println("> " + item);
        // Test available()
        println("Test available: Enter an arbitrary line of text");
        s = "";
        c = Keyboard.readChar(); s += c;
        while(Keyboard.available()>0) {
            c = Keyboard.readChar(); s += c;
        println(s);
}Edited by: corlettk on Oct 1, 2007 1:12 PM