I can't figure out my simple Java homework
I have this programming assignment that converts between meters and feet, and between kilograms and pounds. When I tell the program I want to convert weight (by entering "w" when prompted), it gives me my the following error:
Error: Too many input characters error.
I worked on this for a long time, but can't figure it out. Can someone please tell me how to make the weight conversion work like the length conversion?
import java.util.Scanner;
/**
* This class..
*/
public class UnitConversion3b
{
public static void main(String[] args)
{
Scanner keyboard = new Scanner(System.in);
String maxInputWarning = "\nError: Too many input characters."
+ "\nProgram is now terminating.";
String lengthOrWeight;
final double LENGTH_CONVERSION_FACTOR = 3.2808399;
final double WEIGHT_CONVERSION_FACTOR = 2.20462;
String whichWeightConversion = "empty" , whichLengthConversion = "empty";
double feet = 0, meters = 0, pounds =0 , kilograms = 0;
double metersConvertedToFeet, feetConvertedToMeters;
double poundsConvertedToKilograms, kilogramsConvertedToPounds;
System.out.println("");
System.out.print("What kind of value would you like to convert?");
System.out.print("\nEnter L for length, or W for weight: ");
lengthOrWeight = keyboard.nextLine();
if (lengthOrWeight.length() > 1 ) {
System.out.println(maxInputWarning);
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if ((!(lengthOrWeight.equalsIgnoreCase("l"))
&& (!(lengthOrWeight.equalsIgnoreCase("w"))))){
System.out.println("\nError: Unrecognized conversion type."
+ "\nProgram is now terminating.");
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (lengthOrWeight.equalsIgnoreCase("l")){
System.out.println("\nConverting feet or meters?");
System.out.print("Enter F to convert feet, or M for meters: ");
whichLengthConversion = keyboard.nextLine();
}
if (whichLengthConversion.length() > 1 ) {
System.out.println(maxInputWarning);
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if ((!(whichLengthConversion.equalsIgnoreCase("f"))
&& (!(whichLengthConversion.equalsIgnoreCase("m"))))){
System.out.println("\nError: Unrecognized unit of "
+ "measurement.\nProgram is now terminating." );
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (whichLengthConversion.equalsIgnoreCase("f")){
System.out.print ("Enter the number of feet to"
+ " convert to meters: ");
feet = keyboard.nextDouble();
feetConvertedToMeters = feet / LENGTH_CONVERSION_FACTOR;
System.out.println("The number of meters in " + feet +
" feet is " + feetConvertedToMeters + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (whichLengthConversion.equalsIgnoreCase("m")){
System.out.print ("Enter the number of meters to"
+ " convert to feet: ");
meters = keyboard.nextDouble();
metersConvertedToFeet = meters * LENGTH_CONVERSION_FACTOR;
System.out.println("The number of feet in " + meters +
" meters is " + metersConvertedToFeet + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
}
if (lengthOrWeight.equalsIgnoreCase("w")){
System.out.println("Converting pounds or kilograms?");
System.out.print("Enter P to convert pounds, or K for kilograms: ");
whichWeightConversion = keyboard.nextLine();
}
if (whichWeightConversion.length() > 1 ) {
System.out.println(maxInputWarning);
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if ((!(whichWeightConversion.equalsIgnoreCase("p"))
&& (!(whichWeightConversion.equalsIgnoreCase("k"))))){
System.out.println("\nError: Unrecognized unit of "
+ "measurement.\nProgram is now terminating." );
System.out.print("Press Enter to continue ... ");
return;
} else if (whichWeightConversion.equalsIgnoreCase("p")){
System.out.println("Enter the number of pounds to"
+ " convert to kilograms:");
pounds = keyboard.nextDouble();
poundsConvertedToKilograms = pounds / WEIGHT_CONVERSION_FACTOR;
System.out.println("The number of开发者_JAVA百科 pounds in " + kilograms +
" kilograms is " + poundsConvertedToKilograms + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (whichLengthConversion.equalsIgnoreCase("k")){
System.out.print ("Enter the number of kilograms to"
+ " convert to pounds: ");
kilograms = keyboard.nextDouble();
kilogramsConvertedToPounds = kilograms * WEIGHT_CONVERSION_FACTOR;
System.out.println("The number of pounds in " + pounds +
"pounds is " + kilogramsConvertedToPounds + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else{
return;
}
}
}
You made lots of errors by not changing the code while copy pasting the logic from one place to the other. Your code can be improved a lot by reducing the repetitions and I will be more optimistic in my 'if' 'else' conditions to capture the right cases first and leaving all the wrong cases to the end...Below is the working version of your code modified slightly by fixing the typos and order of the logic.
import java.util.Scanner;
public class UnitConversion3b {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
String maxInputWarning = "\nError: Too many input characters."
+ "\nProgram is now terminating.";
String lengthOrWeight;
final double LENGTH_CONVERSION_FACTOR = 3.2808399;
final double WEIGHT_CONVERSION_FACTOR = 2.20462;
String whichWeightConversion = "empty", whichLengthConversion = "empty";
double feet = 0, meters = 0, pounds = 0, kilograms = 0;
double metersConvertedToFeet, feetConvertedToMeters;
double poundsConvertedToKilograms, kilogramsConvertedToPounds;
System.out.println("");
System.out.print("What kind of value would you like to convert?");
System.out.print("\nEnter L for length, or W for weight: ");
lengthOrWeight = keyboard.nextLine();
if (lengthOrWeight.length() > 1) {
System.out.println(maxInputWarning);
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if ((!(lengthOrWeight.equalsIgnoreCase("l")) && (!(lengthOrWeight
.equalsIgnoreCase("w"))))) {
System.out.println("\nError: Unrecognized conversion type."
+ "\nProgram is now terminating.");
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (lengthOrWeight.equalsIgnoreCase("l")) {
System.out.println("\nConverting feet or meters?");
System.out.print("Enter F to convert feet, or M for meters: ");
whichLengthConversion = keyboard.nextLine();
if (whichLengthConversion.length() > 1) {
System.out.println(maxInputWarning);
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if ((!(whichLengthConversion.equalsIgnoreCase("f")) && (!(whichLengthConversion
.equalsIgnoreCase("m"))))) {
System.out.println("\nError: Unrecognized unit of "
+ "measurement.\nProgram is now terminating.");
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (whichLengthConversion.equalsIgnoreCase("f")) {
System.out.print("Enter the number of feet to"
+ " convert to meters: ");
feet = keyboard.nextDouble();
feetConvertedToMeters = feet / LENGTH_CONVERSION_FACTOR;
System.out.println(feet + " Feet in Meters is "
+ feetConvertedToMeters + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (whichLengthConversion.equalsIgnoreCase("m")) {
System.out.print("Enter the number of meters to"
+ " convert to feet: ");
meters = keyboard.nextDouble();
metersConvertedToFeet = meters * LENGTH_CONVERSION_FACTOR;
System.out.println(meters + " Meters in Feet is "
+ metersConvertedToFeet + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
}
}
else {
System.out.println("Converting pounds or kilograms?");
System.out.print("Enter P to convert pounds, or K for kilograms: ");
whichWeightConversion = keyboard.nextLine();
if (whichWeightConversion.length() > 1) {
System.out.println(maxInputWarning);
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if ((!(whichWeightConversion.equalsIgnoreCase("p")) && (!(whichWeightConversion
.equalsIgnoreCase("k"))))) {
System.out.println("\nError: Unrecognized unit of "
+ "measurement.\nProgram is now terminating.");
System.out.print("Press Enter to continue ... ");
return;
} else if (whichWeightConversion.equalsIgnoreCase("p")) {
System.out.println("Enter the number of pounds to"
+ " convert to kilograms:");
pounds = keyboard.nextDouble();
poundsConvertedToKilograms = pounds / WEIGHT_CONVERSION_FACTOR;
System.out.println(pounds + " Pounds in Kilograms is "
+ poundsConvertedToKilograms + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
} else if (whichWeightConversion.equalsIgnoreCase("k")) {
System.out.print("Enter the number of kilograms to"
+ " convert to pounds: ");
kilograms = keyboard.nextDouble();
kilogramsConvertedToPounds = kilograms
* WEIGHT_CONVERSION_FACTOR;
System.out.println(kilograms + " Kilograms in Pounds is "
+ kilogramsConvertedToPounds + ".");
keyboard.nextLine();
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
}
}
}
}
You're missing a right curly-brace after your meters-to-feet case.
There are some other curly-brace issues throughout your code -- for example, on line 47, there's a right brace where you don't want one. Check over your block structure and, in each case, make sure you're opening and closing blocks where it makes logical sense to do so.
My professor makes us seperate our main class from the Class that is doing the work. It helps a lot. I know it seems like a lot of extra work, but if you pulled your SOPs/inputs out into a DemoMain class and then had your UnitConversion3b class seperate it would be a lot easier to read. Also, I know a lot of people put their {'s right after the close of a paren, but honestly I find my own code a lot easier to read if I drop my opening { down a line. I think your logic is good statement wise, but it's so hard to tell with the brace issues. I think you have some hanging if issues, where you mean to have some of the statements inside a conditional but they are actually outside :-/
Try getting rid of
(!(lengthOrWeight.equalsIgnoreCase("l"))
&& (!(lengthOrWeight.equalsIgnoreCase("w"))))){
and just putting the following block in the else
else{
System.out.println("\nError: Unrecognized conversion type."
+ "\nProgram is now terminating.");
System.out.print("Press Enter to continue ... ");
keyboard.nextLine();
return;
}
It might not help but it will make things clearer.
Also you don't need to check length when you can do line.equalsIgnoreCase("l"), if the input is longer it will not be equal.
The reason why it gives you that error is because Scanner's nextLine() method returns the line as well as the newline character ('\n') that ends the line.
Try this line instead, using String's trim() method to cut off all whitespace from either end :
lengthOrWeight = keyboard.nextLine().trim();
OK, so here is an example of two classes, a main demo class and the actual working class:
TestMain.java goes like this:
import java.util.Scanner;
public class TestMain
{
public static void main(String[] args)
{
float theValue;
float theAnswerIs;
char getLengthOrWeight;
String theValueAsString;
boolean lOrW; //length or width
boolean fOrM; //feet or meters
boolean pOrK; //pounds or kilos... it's a CS joke haha
char getFeetOrMeters;
char getPoundsOrKilos;
//Set up a Scanner instance called keyboard
Scanner keyboard = new Scanner(System.in);
UnitConversion3b converterInstance = new UnitConversion3b();
//Request user for the number to convert
System.out.println("What is the value you will be converting?");
theValueAsString = keyboard.nextLine();
//convert that value and trap
theValue = floatToString(theValueAsString);
//Request user for length or weight conversion
System.out.println("What kind of value would you like to convert?");
System.out.println("Enter L for length, or W for weight: ");
//variable = console.next().charAt(0);
getLengthOrWeight = keyboard.next().charAt(0);
lOrW = converterInstance.lengthOrWeight(getLengthOrWeight);
//create a new UnitConversion3B object and pass it the L or W or bad string the user inputs
//if(true) then user asked for length
if(lOrW)
{
System.out.println("\nConverting feet or meters?");
System.out.print("Enter F to convert feet to meters, or M for meters to feet: ");
//set our main's feetOrMeters variable to the value received when we ask our
//converterInstance the question whichLengthConversion?
getFeetOrMeters = keyboard.next().charAt(0);
fOrM = converterInstance.feetOrMeters(getFeetOrMeters);
//if(fOrM) aka user asked for a length conversion in feet, let's convert it:
if(fOrM)
{
theAnswerIs = (float) (theValue * 3.28083);
System.out.println("The answer is: " + theAnswerIs + " feet.");
}
//if(!fOrM) aka user asked for a length conversion in meters, let's convert it:
if(!fOrM)
{
theAnswerIs = (float) (theValue * 0.3048);
System.out.println("The answer is: " + theAnswerIs + " feet.");
}
//bad input should be trapped in the feetOrMeters function of the converterInstance
}
//if(false) then user asked for weight
else if(!lOrW)
{
System.out.println("Converting pounds or kilograms?");
System.out.print("Enter P to convert pounds to kilos, or K for kilograms to pounds: ");
getPoundsOrKilos = keyboard.next().charAt(0);
pOrK = converterInstance.poundsOrKilos(getPoundsOrKilos);
//if(pOrK) aka user asked for a pounds to kilos conversion, let's convert it:
if(pOrK)
{
theAnswerIs = (float) (theValue * 0.45359237);
System.out.println("The answer is: " + theAnswerIs + " feet.");
}
//if(!pOrK) aka user asked for a kilos to pounds conversion, let's convert it:
if(!pOrK)
{
theAnswerIs = (float) (theValue * 2.20462262);
System.out.println("The answer is: " + theAnswerIs + " feet.");
}
//bad input should be trapped in the poundsOrKilos function of the converterInstance
}
}
private static float floatToString(String theValueAsString) {
// thanks for this method from http://devdaily.com/java/edu/qanda/pjqa00013.shtml
float f = 0;
try
{
f = Float.valueOf(theValueAsString.trim()).floatValue();
}
catch (NumberFormatException nfe)
{
System.out.println("NumberFormatException: " + nfe.getMessage());
}
return f;
}
}
and UnitConversion3b.java goes like:
public class UnitConversion3b
{
private boolean lengthOrWeightSwitch;
boolean feetOrMeters;
final double LENGTH_CONVERSION_FACTOR = 3.2808399;
final double WEIGHT_CONVERSION_FACTOR = 2.20462;
boolean poundsOrKilograms;
public UnitConversion3b(String getLengthOrWeight) {
if(getLengthOrWeight == "W")
lengthOrWeightSwitch = true;
else if(getLengthOrWeight == "L")
lengthOrWeightSwitch = false;
else
{
badInput();
}
}
public boolean getConversionType()
{
return lengthOrWeightSwitch;
}
public boolean whichLengthConversion(String whichLength)
{
if(whichLength == "F")
feetOrMeters = true;
else if(whichLength == "M")
feetOrMeters = false;
else
{
badInput();
}
return feetOrMeters;
}
public boolean whichWeightConversion(String whichWeight)
{
if(whichWeight == "P")
poundsOrKilograms = true;
else if(whichWeight == "K")
poundsOrKilograms = false;
else
{
badInput();
}
return poundsOrKilograms;
}
public void badInput()
{
System.out.println("Invalid input");
System.exit(0);
}
public String valueToFeet(float theValue) {
//assumes value entered need to be converted from meters to feet
return "" + (theValue*LENGTH_CONVERSION_FACTOR);
}
public String valueToMeters(float theValue) {
//assumes value entered need to be converted from feet to meters
return "" + (theValue/LENGTH_CONVERSION_FACTOR);
}
public String valueToPounds(float theValue) {
// assumes value entered needs to be converted to pounds
return ""+ (theValue * WEIGHT_CONVERSION_FACTOR);
}
public String valueToKilos(float theValue) {
// TODO Auto-generated method stub
return ""+ (theValue / WEIGHT_CONVERSION_FACTOR);
}
public void setConversionType(char getLengthOrWeight) {
if(getLengthOrWeight == 'L')
lengthOrWeightSwitch = true;
if(getLengthOrWeight == 'W')
lengthOrWeightSwitch = false;
else
badInput();
}
public boolean lengthOrWeight(char getLengthOrWeight) {
if(getLengthOrWeight == 'L')
return true;
if(getLengthOrWeight == 'W')
return false;
return false;
}
public boolean feetOrMeters(char getFeetOrMeters) {
if(getFeetOrMeters == 'F')
return true;
if(getFeetOrMeters == 'M')
return false;
//these functions return false under 'false' conditions... work on the logic :-)
return false;
}
public boolean poundsOrKilos(char getPoundsOrKilos) {
if(getPoundsOrKilos == 'P')
return true;
if(getPoundsOrKilos == 'K')
return false;
//these functions return false under 'false' conditions... work on the logic :-)
return false;
}
}
Now please note, even if I pasted this correctly you are going to get a worse than bad score on your assignment if you turn in this code. It compiles and runs, but it ignores the max char# input you seemed to have constrained on your assignment. Probably there are other issues, howver, I think it is somewhat followable code. I would probably want to break it even further into more classes, but I hope this helps.
I know this may sound a little nutty, but it works: Imagine your user input as a little animal and you have set a trap for it. You need to catch the animal and do something to it. For our animal lovers' sake, let's say you need to catch it, tranquilize it, weigh it, and put a radio collar on it and then release it relatively unharmed provided it is of type Cougar. So, our trap is a multi-function trap. Whatever enters it, a value will be produced.
WHAM!!! Something is in the trap. Luckily, our trap is automatic. If it doesn't land a float value, then the trap opens and it leaves. It isn't a Cougar.
OK, the trap is still closed. It must be a Cougar. We can work on it.
Now, we ask the guy wearing the Banana Republic gear with the big Nikon around his neck for some help. We have this Float value in the trap. Now, we ask the Scientist in the Banana Repubic gear what our number means.
"Hey, Scientist Guy, what does the number in our trap mean?"
If "It's the length", he answers:
This is the length of the Cougar in feet, I need it it converted to meters...
This is the length of the Cougar in meters, I need it it converted to feet...
If "it's the weight", he answers:
This is the weight in pounds, I need it converted to kilos...
This is the weight in kilos, I need it converted to pounds...
You may find that, when you think about it, your Teacher was asking 'how do you set up the problem'? In other words, by asking the user for the value first, you can cut down on the amount of questions the program has to answer.
加载中,请稍侯......
精彩评论