Having trouble with program output an printf [dupl

问题:

This question already has an answer here:

• How do I compare strings in Java? 23 answers

I am writing a program where it takes a file and tries to use data from the file in order to create an output.

this is the program:

import java.util.Scanner;
import java.io.*;


 public class WebberProjectTest
 {

 public static void main(String[] args) throws IOException 
 {

 Scanner scanner = new Scanner(new File("portlandvip.txt"));
 while (scanner.hasNext())
  {
 String firstName = scanner.next();
 String lastName = scanner.next();
 Integer number = scanner.nextInt();
 String ticketType = scanner.next();

 if(ticketType == "Court")
 {
 Integer a = 75 * number;
 System.out.println(" " + firstName + " " + lastName + " " + a);            
 scanner.nextLine();  
 }

 if(ticketType == "Box")
 {
 Integer a = 50 * number;
 System.out.println(" " + firstName + " " + lastName + " " + a);            
 scanner.nextLine();  
 }

 if(ticketType == "Club")
 {
Integer a = 40 * number;
System.out.println(" " + firstName + " " + lastName + " " + a);            
 scanner.nextLine();  
  }


}       

  }    
}

This is the data file:

Loras Tyrell 5 Club

Margaery Tyrell 8 Box

Roslin Frey 2 Box

Sansa Stark 2 Club

Jon Snow 5 Club

Edmure Tully 3 Box

Joffrey Baratheon 20 Court

Stannis Baratheon 4 Club

Jaime Lannister 2 Box

Cersei Lannister 1 Court

Beric Dondarrion 8 Court

Balon Greyjoy 16 Box

Olenna Tyrell 4 Court

Mace Tyrell 5 Box

Tyrion Lannister 2 Club

Sandor Clegane 2 Court

Gregor Clegane 6 Club

Samwell Tarly 3 Club

Petyr Baelish 6 Court

The purpose of this program is to that the input File and output for example.

Input: Loras Tyrell 5 Court

Output: Loras Tyrell $375.00

However, when i run the program, nothing happens. I have a few ideas on why this is happening, but i dont know how to fix it, any help would be appreciated.

I also have another question about printf statements. I altered the program so that it prints correctly, but now i have to change the println statements to printf statements. this is what i changed the program to look like now:

import java.util.Scanner;
import java.io.*;


public class WebberProjectTest
{

public static void main(String[] args) throws IOException 
{

Scanner scanner = new Scanner(new File("portlandvip.txt"));
while(scanner.hasNext()) 
{
String line = scanner.nextLine();
String[] words = line.split(" "); 

if(words[3].equals("Court")) 
{
    int a = 75 * Integer.parseInt(words[2]);
    System.out.printf(" " + words[0] + " " + words[1] + " $%.2f\n ", a);
}

if(words[3].equals("Box")) 
{
    int a = 50 * Integer.parseInt(words[2]);
    System.out.printf(" " + words[0] + " " + words[1] + " $%.2f\n", a);
}

if(words[3].equals("Club")) 
{
    int a = 40 * Integer.parseInt(words[2]);
    System.out.printf(" " + words[0] + " " + words[1] + " $%.2f\n", a);
}
}       


 }    
} 

and this is what prints out:

Loras Tyrell Loras Tyrell $java.util.IllegalFormatConversionException: f !=         java.lang.Integer
at java.util.Formatter$FormatSpecifier.failConversion(Unknown Source)
at java.util.Formatter$FormatSpecifier.printFloat(Unknown Source)
at java.util.Formatter$FormatSpecifier.print(Unknown Source)
at java.util.Formatter.format(Unknown Source)
at java.io.PrintStream.format(Unknown Source)
at java.io.PrintStream.printf(Unknown Source)
at WebberProjectTest.main(WebberProjectTest.java:32)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)

I dont know what i did wrong in the printf statement, thank you for any assistance.

回答1:

Try reading line at once and then split the elements.. Something like this

while(inp.hasNext()) {
    String line = inp.nextLine();
    String[] words = line.split(" ");            
    if(words[3].equals("Court")) {
        int a = 75 * Integer.parseInt(words[2]);
        System.out.println(" " + words[0] + " " + words[1] + " " + a);
    }
    // ....other if conditions
    if(inp.hasNext())   //to skip over empty line
        inp.nextLine();
}

回答2:

Strings should be compared with the equals() method instead of the == operator. e.g.,

ticketType.equals("Court") //instead of ==> ticketType == "Court"

回答3:

Try this code.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
import java.util.StringTokenizer;


public class test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        try {
            Scanner scanner = new Scanner(new File("test.txt"));
            while (scanner.hasNext()){
                String string = scanner.useDelimiter("\n").next();

                if(!string.equals(" ") && !string.equals("\n") && !string.equals("") && !string.equals("\r") ){
                    StringTokenizer st = new StringTokenizer(string," ");
                    String firstName = "";
                    String lastName = "";
                    Integer number = 0;
                    String ticketType = "";
                    while (st.hasMoreElements()) {
                        firstName = st.nextElement().toString();
                        lastName = st.nextElement().toString();
                        number = Integer.parseInt(st.nextElement().toString());
                        ticketType = st.nextElement().toString().trim();
                        System.out.println(" " + firstName + " " + lastName + " " + number + " " +ticketType); 
                    }
                    if(ticketType.equalsIgnoreCase("Court"))
                    {
                        Integer a = 75 * number;
                        System.out.println(" " + firstName + " " + lastName + " " + a);  
                    }
                    else if(ticketType.equalsIgnoreCase("Box"))
                    {
                        Integer a = 50 * number;
                        System.out.println(" " + firstName + " " + lastName + " " + a);   
                    }
                    else if(ticketType.equalsIgnoreCase("Club"))
                    {
                        Integer a = 40 * number;
                        System.out.println(" " + firstName + " " + lastName + " " + a);            
                    }
                }//if(!string.equals(" "))

            }//while
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}