Showman
Reputation: 55
Program Misidentifies the Char
StackOverflow community. I'm trying to create a command line application for the manipulation of X and Y coordinates. What confuses me is that when it asks for X or Y under case B, it thinks that I typed in something other than X or Y when I haven't typed in anything at all. What could be making this happen?
public class OrderedPairTest {
public static void main(String[] args) {
OrderedPair op1 = new OrderedPair();
OrderedPair op2 = new OrderedPair();
OrderedPair op3 = new OrderedPair();
EasyReader console = new EasyReader();
System.out.println("Ordered Pairs 1, 2, and 3 are set to (0,0).\nWhat would you like to do?");
System.out.println("Type A to display values, B for setting values, C for moving values,\nD for string conversion, E for printing, and F for other calculations.");
char one = console.readChar();
switch(one){
case 'A':
System.out.print("Type the ordered pair's number: ");
int onea = console.readInt();
switch(onea){
case 1:
op1.getX();
op1.getY();
break;
case 2:
op2.getX();
op2.getY();
break;
case 3:
op3.getX();
op3.getY();
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
main(null);
case 'B':
System.out.print("Type the ordered pair's number: ");
int oneb = console.readInt();
switch(oneb){
case 1:
System.out.print("\nX or Y?");
char twoa = console.readChar();
switch(twoa){
case 'X':
System.out.print("\nValue? ");
int valx1 = console.readInt();
op1.setX(valx1);
break;
case 'Y':
System.out.print("\nValue? ");
int valy1 = console.readInt();
op1.setY(valy1);
break;
default:
System.out.println("\nInvalid axis. Returning to the main menu.");
main(null);
}
break;
case 2:
System.out.println("X or Y?");
char twob = console.readChar();
switch(twob){
case 'X':
System.out.println("Value?");
int valx2 = console.readInt();
op1.setX(valx2);
break;
case 'Y':
System.out.println("Value?");
int valy2 = console.readInt();
op1.setY(valy2);
break;
default:
System.out.println("Invalid axis. Returning to the main menu.");
main(null);
}
break;
case 3:
System.out.println("X or Y?");
char twoc = console.readChar();
switch(twoc){
case 'X':
System.out.println("Value?");
int valx3 = console.readInt();
op1.setX(valx3);
break;
case 'Y':
System.out.println("Value?");
int valy3 = console.readInt();
op1.setY(valy3);
break;
default:
System.out.println("Invalid axis. Returning to the main menu.");
main(null);
}
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
main(null);
case 'C':
System.out.print("Type the ordered pair's number: ");
int onec = console.readInt();
switch(onec){
case 1:
System.out.println("X, Y or B (Both)?");
char twoa = console.readChar();
switch(twoa){
case 'X':
System.out.println("Value?");
int valx1 = console.readInt();
op1.moveX(valx1);
break;
case 'Y':
System.out.println("Value?");
int valy1 = console.readInt();
op1.moveY(valy1);
break;
case 'B':
System.out.println("Value of X?");
int valx4 = console.readInt();
System.out.println("Value of Y?");
int valy4 = console.readInt();
op1.moveXY(valx4,valy4);
break;
default:
System.out.println("Invalid axis. Returning to the main menu.");
main(null);
}
break;
case 2:
System.out.println("X or Y?");
char twob = console.readChar();
switch(twob){
case 'X':
System.out.println("Value?");
int valx5 = console.readInt();
op1.moveX(valx5);
break;
case 'Y':
System.out.println("Value?");
int valy5 = console.readInt();
op1.moveY(valy5);
break;
case 'B':
System.out.println("Value of X?");
int valx2 = console.readInt();
System.out.println("Value of Y?");
int valy2 = console.readInt();
op1.moveXY(valx2,valy2);
break;
default:
System.out.println("Invalid axis. Returning to the main menu.");
main(null);
}
break;
case 3:
System.out.println("X or Y?");
char twoc = console.readChar();
switch(twoc){
case 'X':
System.out.println("Value?");
int valx3 = console.readInt();
op1.moveX(valx3);
break;
case 'Y':
System.out.println("Value?");
int valy3 = console.readInt();
op1.moveY(valy3);
break;
case 'B':
System.out.println("Value of X?");
int valx6 = console.readInt();
System.out.println("Value of Y?");
int valy6 = console.readInt();
op1.moveXY(valx6,valy6);
break;
default:
System.out.println("Invalid axis. Returning to the main menu.");
main(null);
}
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
main(null);
case 'D':
System.out.print("Type the ordered pair's number: ");
int oned = console.readInt();
switch(oned){
case 1:
op1.toString();
break;
case 2:
op2.toString();
break;
case 3:
op3.toString();
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
main(null);
case 'E':
System.out.print("Type the ordered pair's number: ");
int onee = console.readInt();
switch(onee){
case 1:
op1.printOP();
break;
case 2:
op2.printOP();
break;
case 3:
op3.printOP();
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
main(null);
case 'F':
System.out.print("Type the first ordered pair's number: ");
int onef = console.readInt();
System.out.print("\nType the second ordered pair's number: ");
int oneg = console.readInt();
switch(onef){
case 1:
switch(oneg){
case 2:
op1.distance(op2);
op1.midpoint(op2);
break;
case 3:
op1.distance(op3);
op1.midpoint(op3);
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
case 2:
switch(oneg){
case 1:
op2.distance(op1);
op2.midpoint(op1);
break;
case 3:
op2.distance(op3);
op2.midpoint(op3);
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
case 3:
switch(oneg){
case 1:
op3.distance(op1);
op3.midpoint(op1);
break;
case 2:
op3.distance(op2);
op3.midpoint(op2);
break;
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
default:
System.out.println("Invalid pair number. Returning to main menu.");
main(null);
}
main(null);
default:
System.out.println("Invalid option. Returning to main menu.");
main(null);
}
}
}
Here is my EasyReader class for debugging purposes. It isn't mine, but it streamlines reading strings, ints, and chars:
public class EasyReader
{
protected String myFileName;
protected BufferedReader myInFile;
protected int myErrorFlags = 0;
protected static final int OPENERROR = 0x0001;
protected static final int CLOSEERROR = 0x0002;
protected static final int READERROR = 0x0004;
protected static final int EOF = 0x0100;
/**
* Constructor. Prepares console (System.in) for reading
*/
public EasyReader()
{
myFileName = null;
myErrorFlags = 0;
myInFile = new BufferedReader(
new InputStreamReader(System.in), 128);
}
/**
* Constructor. opens a file for reading
* @param fileName the name or pathname of the file
*/
public EasyReader(String fileName)
{
myFileName = fileName;
myErrorFlags = 0;
try
{
myInFile = new BufferedReader(new FileReader(fileName), 1024);
}
catch (FileNotFoundException e)
{
myErrorFlags |= OPENERROR;
myFileName = null;
}
}
/**
* Closes the file
*/
public void close()
{
if (myFileName == null)
return;
try
{
myInFile.close();
}
catch (IOException e)
{
System.err.println("Error closing " + myFileName + "\n");
myErrorFlags |= CLOSEERROR;
}
}
/**
* Checks the status of the file
* @return true if en error occurred opening or reading the file,
* false otherwise
*/
public boolean bad()
{
return myErrorFlags != 0;
}
/**
* Checks the EOF status of the file
* @return true if EOF was encountered in the previous read
* operation, false otherwise
*/
public boolean eof()
{
return (myErrorFlags & EOF) != 0;
}
private boolean ready() throws IOException
{
return myFileName == null || myInFile.ready();
}
/**
* Reads the next character from a file (any character including
* a space or a newline character).
* @return character read or <code>null</code> character
* (Unicode 0) if trying to read beyond the EOF
*/
public char readChar()
{
char ch = '\u0000';
try
{
if (ready())
{
ch = (char)myInFile.read();
}
}
catch (IOException e)
{
if (myFileName != null)
System.err.println("Error reading " + myFileName + "\n");
myErrorFlags |= READERROR;
}
if (ch == '\u0000')
myErrorFlags |= EOF;
return ch;
}
/**
* Reads from the current position in the file up to and including
* the next newline character. The newline character is thrown away
* @return the read string (excluding the newline character) or
* null if trying to read beyond the EOF
*/
public String readLine()
{
String s = null;
try
{
s = myInFile.readLine();
}
catch (IOException e)
{
if (myFileName != null)
System.err.println("Error reading " + myFileName + "\n");
myErrorFlags |= READERROR;
}
if (s == null)
myErrorFlags |= EOF;
return s;
}
/**
* Skips whitespace and reads the next word (a string of consecutive
* non-whitespace characters (up to but excluding the next space,
* newline, etc.)
* @return the read string or null if trying to read beyond the EOF
*/
public String readWord()
{
StringBuffer buffer = new StringBuffer(128);
char ch = ' ';
int count = 0;
String s = null;
try
{
while (ready() && Character.isWhitespace(ch))
ch = (char)myInFile.read();
while (ready() && !Character.isWhitespace(ch))
{
count++;
buffer.append(ch);
myInFile.mark(1);
ch = (char)myInFile.read();
};
if (count > 0)
{
myInFile.reset();
s = buffer.toString();
}
else
{
myErrorFlags |= EOF;
}
}
catch (IOException e)
{
if (myFileName != null)
System.err.println("Error reading " + myFileName + "\n");
myErrorFlags |= READERROR;
}
return s;
}
/**
* Reads the next integer (without validating its format)
* @return the integer read or 0 if trying to read beyond the EOF
*/
public int readInt()
{
String s = readWord();
if (s != null)
return Integer.parseInt(s);
else
return 0;
}
/**
* Reads the next double (without validating its format)
* @return the number read or 0 if trying to read beyond the EOF
*/
public double readDouble()
{
String s = readWord();
if (s != null)
return Double.parseDouble(s);
// in Java 1, use: return Double.valueOf(s).doubleValue();
else
return 0.0;
}
}
And finally, here's my OrderedPair class:
public class OrderedPair {
int a,b;
String q = "";
public int getX() {
System.out.println("X is "+a);
return a;
}
public int getY() {
System.out.println("Y is "+b);
return b;
}
public void setX(int x) {
a = x;
System.out.println("X has been set to "+a);
if (b != 0) setQ();
else;
}
public void setY(int y) {
b = y;
System.out.println("Y has been set to "+b);
if (a != 0) setQ();
else;
}
public String toString() {
String msg = ("("+a+","+b+") Q"+q);
System.out.println("Values have been converted into string.");
return msg;
}
public int moveX(int amt) {
a+=amt;
System.out.println("X has been moved "+amt+" units.");
if ((b != 0) && (a != 0)) setQ();
else;
return a;
}
public int moveY(int amt) {
b+=amt;
System.out.println("Y has been moved "+amt+" units.");
if ((b != 0) && (a != 0)) setQ();
else;
return b;
}
public void moveXY(int amt1, int amt2){
a+=amt1;
b+=amt2;
System.out.println("X has been moved "+amt1+" units.");
System.out.println("Y has been moved "+amt2+" units.");
if ((b != 0) && (a != 0)) setQ();
else;
}
public void distance(OrderedPair other) {
double d = Math.sqrt(Math.pow(other.b-this.b,2)+Math.pow(other.a-this.a,2));
System.out.println("The distance between the two points is: "+d);
}
public void midpoint(OrderedPair other) {
int x3 = (this.a+other.a)/2;
int y3 = (this.b+other.b)/2;
System.out.println("The midpoint is at: ("+x3+","+y3+")");
}
public void printOP() {
if (q!= "") System.out.println("("+a+","+b+") Q"+q);
else System.out.println("Q has not been set.");
}
private void setQ() {
if ((a!=0)&&(b!=0)){
if (a > 0){
if (b > 0) q = "I";
else q = "IV";
}
else {
if (b > 0) q = "II";
else q = "III";
}
System.out.println("The quadrant has been set.");
}
else System.out.println("X and/or Y are zero, please assign the variables a nonzero value.");
}
}
Upvotes: 0
Views: 114
Answers (2)
George Tomlinson
Reputation: 1931
It's reading white space. If you insert
console.readLine();
this reads the unwanted stuff and then you can use your code as you wanted to. Modify your code as follows for case 1 (and similarly for cases 2 and 3) and it works:
case 1:
System.out.print("\nX or Y?");
console.readLine();
char twoa = console.readChar();
I found this out by inserting the line
System.out.println("twoa: "+twoa);
at the right point in your code (see below)
case 1:
System.out.print("\nX or Y?");
char twoa = console.readChar();
System.out.println("twoa: "+twoa);
The results of running the program were then as follows:
Ordered Pairs 1, 2, and 3 are set to (0,0).
What would you like to do?
Type A to display values, B for setting values, C for moving values,
D for string conversion, E for printing, and F for other calculations.
B
Type the ordered pair's number: 1
X or Y?
twoa:
Invalid axis. Returning to the main menu.
Ordered Pairs 1, 2, and 3 are set to (0,0).
What would you like to do?
Type A to display values, B for setting values, C for moving values,
D for string conversion, E for printing, and F for other calculations.
Notice the line
twoa:
which reveals that console.readChar() reads white space and then assigns it to the char 'twoa' in the line
char twoa = console.readChar();
If you want to understand what programs are doing, inserting such print statements helps.
Upvotes: 0
dataNinja124
Reputation: 130
Try adding console.skipLine(); before you read in the char. As a commentor noted, you are probably reading in the endOfLine character when you use readChar (but it would be easier to debug if you posted complete, compilable code including your class definitions.)
Upvotes: 1
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