-2
import java.io.*;
// A binary stream is a series of data type values
// To read and write to them you use different methods
// based on the type of data that you are using
public class lesson33{
public static void main(String[] args){
// Create an array of type Customer
Customer[] customers = getCustomers();
// A DataOutputStream allows you to print
// primitive data types to a file
DataOutputStream custOutput = createFile("/Users/derekbanas/Documents/workspace3/Java Code/src/customers.dat");
// Enhanced for loop for arrays
// Cycles through all of the people in the customers array
for(Customer person : customers){
createCustomers(person, custOutput);
}
// Closes the connection to the DataOutputStream
try {
custOutput.close();
} catch (IOException e) {
System.out.println("An I/O Error Occurred");
// Closes the program
System.exit(0);
}
getFileInfo();
}
// class that defines all the fields for my customers
private static class Customer{
public String custName;
public int custAge;
public double custDebt;
public boolean oweMoney;
public char custSex;
// constructor that's called when a customer is made
public Customer(String custName, int custAge, double custDebt, boolean oweMoney, char custSex){
this.custName = custName; // String
this.custAge = custAge; // Integer
this.custDebt = custDebt; // Double
this.oweMoney = oweMoney; // Boolean
this.custSex = custSex; // Character
}
}
// Creates an array of Customer Objects
private static Customer[] getCustomers(){
Customer[] customers = new Customer[5];
customers[0] = new Customer("John Smith", 21, 12.25, true, 'M');
customers[1] = new Customer("Sally Smith", 30, 2.25, true, 'F');
customers[2] = new Customer("Paul Ryan", 21, 0, false, 'M');
customers[3] = new Customer("Mark Jacobs", 21, 3.25, true, 'M');
customers[4] = new Customer("Steve Nash", 21, 5.25, true, 'M');
return customers;
}
// Create the file and the DataOutputStream that will write to the file
private static DataOutputStream createFile(String fileName){
try{
// Creates a File object that allows you to work with files
// on the hard drive. There is no difference between File
// for character or binary stream writing, or reading
File listOfNames = new File(fileName);
// FileOutputStream is used to write streams of data to a file
// You define whether a new file is created versus appended
// to based on if you add a boolean to the FileOutputStream
// FileOutputStream(file, true) : Appends to the file
// FileOutputStream(file, false) : Creates a new file
// BufferedOutputStream gathers all the data and then writes
// it all at one time (Speeds up the Program)
// DataOutputStream is used to write primitive data to the file
DataOutputStream infoToWrite = new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream(listOfNames)));
return infoToWrite;
}
// You have to catch this when you call FileWriter
catch(IOException e){
System.out.println("eager");
System.out.println("An I/O Error Occurred");
// Closes the program
System.exit(0);
}
return null;
}
// Create a string with the customer info and write it to the file
private static void createCustomers(Customer customer, DataOutputStream custOutput){
try{
// Write primitive data to the file
// Writes a String in UTF format
custOutput.writeUTF(customer.custName);
// Writes an Integer
custOutput.writeInt(customer.custAge);
// Writes a Double
custOutput.writeDouble(customer.custDebt);
// Writes a Boolean
custOutput.writeBoolean(customer.oweMoney);
// Writes a Character
custOutput.writeChar(customer.custSex);
// You also have writeByte, writeFloat, writeLong
// and writeShort
}
catch(IOException e){
System.out.println("eager 1");
System.out.println("An I/O Error Occurred");
System.exit(0);
}
}
// Read info from the file and write it to the screen
private static void getFileInfo(){
System.out.println("Info Written to File\n");
// Open a new connection to the file
File listOfNames = new File("/Users/derekbanas/Documents/workspace3/Java Code/src/customers.dat");
boolean eof = false;
try {
// A DataInputStream object has the methods for reading the data
// The BufferedInputStream gathers the data in blocks
// FileInputStream gets data from the file
DataInputStream getInfo = new DataInputStream(
new BufferedInputStream(
new FileInputStream(listOfNames)));
// Using a while loop that pulls data until EOFException is thrown
while (!eof){
// You have to read data in the exact order it was put in the file
String custName = getInfo.readUTF();
int custAge = getInfo.readInt();
double custDebt = getInfo.readDouble();
boolean oweMoney = getInfo.readBoolean();
char custSex = getInfo.readChar();
System.out.println(custName);
System.out.println(custAge);
System.out.println(custDebt);
System.out.println(oweMoney);
System.out.println(custSex + "\n");
}
getInfo.close();
} // END OF TRY
catch (EOFException e) {
eof = true;
}
// Can be thrown by FileInputStream
catch (FileNotFoundException e) {
System.out.println("Couldn't Find the File");
System.exit(0);
}
catch(IOException e){
System.out.println("eager 2");
System.out.println("An I/O Error Occurred");
System.exit(0);
}
}
}
產生輸出如下： -我不明白這個程序中發生了什麼問題，請幫助我？
eager
An I/O Error Occurred
這個程序的目的是要打印的客戶證書表示DataInputStream所
二進制流是一系列數據類型的值 //要讀取和寫給他們你使用不同的方法 //根據你使用的數據類型
那麼你認爲什麼是錯的？你沒有告訴我們。 – 2015-01-09 20:48:03
你抓住了，但你爲什麼不打印堆棧跟蹤？這就是所有信息都隱藏起來的地方！ – MightyPork 2015-01-09 20:51:15
我們沒有辦法告訴你什麼時候吞下例外。可能是任何事情。 – 2015-01-09 20:52:10