昨天我有一个问题，对于我在工作中所做的项目有一个迅速而有用的答案，所以今天我想我会再试一次我的另一个问题。
我的项目是采取一个＆＃34; ACH＆＃34;文件（只是一个固定格式的文本文件）使用GUI，处理它，重新格式化数据（一些复制一次，一些不复制，一些不复制），最后导出到一个新的.ACH文件。
我首先要举一个我将要使用的文件类型的例子，这只是一个例子，因为我无法在线发布真正的ACH文件。
111111111111111111111111
522293884838383848484838483884
62837717273727
62993304993918
621272773727755828
821200303299191
90000000000000000000000000
99999999999999999999999999
99999999999999999999999999
＆＃34;处理＆＃34;要求我批量生产＃34;上面的数据格式我把它放在＆＃34; clusters＆＃34; 5-6-8与＆＃34; 5＆＃34;和＆＃34; 8＆＃34;每个群集的数量相同，并使用列表中的每个六个，例如：
522293884838383848484838483884
62837717273727
821200303299191
522293884838383848484838483884
62993304993918
821200303299191
//and so on
我创建了一个程序，允许我（几乎）实现这个但我遇到了一个问题 - 一个＆＃34; nullpointerexception＆＃34;。在我开始进一步解释之前，我的问题允许我发布我的代码：
package nacha;
import java.io.*;
import javax.accessibility.Accessible;
import javax.swing.JComponent;
import javax.swing.JFileChooser;
import javax.swing.filechooser.FileNameExtensionFilter;
public class Nacha extends JComponent implements Accessible
{
public static void main(String args[])
{
String five = null;
String eight = null;
BufferedReader br = null;
BufferedWriter bw = null;
int count1 = 0;
int count2 = 0; //Counter variables for the numbers that should only
int count3 = 0; //be called from the ACH once.
//Used for later constructing of the output file.
//GUI stuff below for the input file
JFileChooser chooser = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter("TXT & ACH Files", "txt", "ach");
chooser.setFileFilter(filter);
chooser.setDialogTitle("Please choose ACH file to upload");
int returnVal = chooser.showOpenDialog(chooser);
if(returnVal == JFileChooser.APPROVE_OPTION)
{
try{ //Section for the buffer reader/writer.
String sCurrentLine;
br = new BufferedReader(new FileReader(chooser.getSelectedFile()));
bw = new BufferedWriter(new FileWriter(chooser.getCurrentDirectory()+"//NachaOutput.ACH"));
while((sCurrentLine = br.readLine()) !=null)
{
//Below is conditional statements that check to see if the line contains certain
//characters. If they do the it takes the lines and writes them to a new
//document (set above). It also adds +1 to the counter so the same numbers
//will not be written twice.
System.out.println(sCurrentLine);
if (sCurrentLine.startsWith("5")){
count1++;
bw.write(sCurrentLine);
bw.newLine();
five = sCurrentLine;
}else if (sCurrentLine.startsWith("6") && count2 == 0){
count2++;
bw.write(sCurrentLine);
bw.newLine();
}else if (sCurrentLine.startsWith("8")){
count3++;
bw.write(sCurrentLine);
bw.newLine();
eight = sCurrentLine;
}else if(sCurrentLine.startsWith("6") && count2 ==1){
bw.write(five);
bw.write(sCurrentLine);
bw.write(eight);
}else{
}
}
}catch (IOException e){
e.printStackTrace();
} finally {
try {
if (br != null)br.close();
if (bw != null)bw.close();
}catch (IOException ex){
ex.printStackTrace();
}
}
}
}
}
假设我只有一个＆＃34; 6＆＃34;我的原始文件中的数字，该程序工作正常。当我有一个以上的时候会出现这个问题，因为我没有办法（我知道）要重新调整＆＃34; 5＆＃34;和＆＃34; 8＆＃34;数不止一次。我最初的计划是复制＆＃34; sCurrentLine＆＃34;字符串分为两个字符串，称为＆＃34;五个＆＃34;和＆＃34;八＆＃34;这可以在以后轻松引用，并在每个＆＃34; 6＆＃34;之前和之后输入它们的值。文本文件中剩余的数字如下所示：
if (sCurrentLine.startsWith("5")){
count1++;
bw.write(sCurrentLine);
bw.newLine();
five = sCurrentLine;
和
}else if (sCurrentLine.startsWith("8")){
count3++;
bw.write(sCurrentLine);
bw.newLine();
eight = sCurrentLine;
我会在这里使用这些值：
}else if(sCurrentLine.startsWith("6") && count2 ==1){
bw.write(five);
bw.write(sCurrentLine);
bw.write(eight);
我得到了一个＆＃34; nullpointer＆＃34;我尝试写入（五）变量的行上的错误，该变量应该包含我设置＆＃34;五＆＃34;时的sCurrentLine的值。变量。 （所以它应该简单地发布一个＆＃34; 5 somtething＆＃34;数字。无论我尝试了多少种方法，我都无法找到一种方法来制作＆＃34;五＆＃34;等于sCurrentLine而不会产生错误我也尝试过使用PrintScreen来检查我设置的方法＆＃34; 5＆＃34;它实际上确实设置成功，所以我完全迷失了如何纠正这种情况。
我希望有人可以提供我如何纠正这个问题。这是一项工作任务，而不是随意的，我很想解决这个问题。
提前致谢，如果您需要更多信息，请告诉我们！
编辑：我道歉：这是例外：
Exception in thread "main" java.lang.NullPointerException
at java.io.Writer.write(Unknown Source)
at nacha.Nacha.main(Nacha.java:83)
标记为：
bw.write(eight);
答案 0 :(得分：2)
if (sCurrentLine.startsWith("5")){
count1++;
bw.write(sCurrentLine);
bw.newLine();
five = sCurrentLine;
}else if (sCurrentLine.startsWith("6") && count2 == 0){
count2++;
bw.write(sCurrentLine);
bw.newLine();
}else if (sCurrentLine.startsWith("8")){
count3++;
bw.write(sCurrentLine);
bw.newLine();
eight = sCurrentLine;
}else if(sCurrentLine.startsWith("6") && count2 ==1){
bw.write(five);
bw.write(sCurrentLine);
bw.write(eight);
}
注意在第一个if语句中，设置变量5。
五现在有一个值，所以它不是null。
您永远不会将八个值设置为值，因此它仍为null。
此程序后的程序流程：
111111111111111111111111
522293884838383848484838483884
62837717273727
62993304993918
621272773727755828
821200303299191
90000000000000000000000000
99999999999999999999999999;
99999999999999999999999999
您首先到达第一个if语句，将五个设置为“522293884838383848484838483884”
达到第二个if语句，将“62837717273727”打印到文件。
未达到第三个if语句，因为“62993304993918”以6开头，而不是8开始。
然后达到第四个if语句，尝试写入五个变量，当前行和一个null 8变量。
我建议创建一个字符串ArrayList，对于以6开头的每一行，将字符串添加到arraylist。然后，当你设置五和八时，迭代arraylist并按你认为合适的方式写作。
ArrayList <String> sixValues = new ArrayList();
if(sCurrentLine.startsWith("6"){
sixValues.add(sCurrentLine);
}
和for-loop
for( String s : sixValues){
bw.write(five);
bw.write(sCurrentLine);
bw.write(eight);
}
答案 1 :(得分：0)
感谢Psychrom帮助我找到这个解决方案，他的回答是100％正确的我需要做的事情我希望我可以给他一些声誉，但我不能。
这是我的最终工作代码FYI：
package nacha;
import java.awt.List;
import java.io.*;
import java.util.ArrayList;
import javax.accessibility.Accessible;
import javax.swing.JComponent;
import javax.swing.JFileChooser;
import javax.swing.filechooser.FileNameExtensionFilter;
public class Nacha extends JComponent implements Accessible
{
public static void main(String args[])
{
ArrayList<String> list = new ArrayList<String>();
String five = null;
String eight = null;
BufferedReader br = null;
BufferedWriter bw = null;
int count1 = 0;
int count2 = 0; //Counter variables for the numbers that should only
int count3 = 0; //be called from the ACH once.
//Used for later constructing of the output file.
//GUI stuff below for the input file
JFileChooser chooser = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter("TXT & ACH Files", "txt", "ach");
chooser.setFileFilter(filter);
chooser.setDialogTitle("Please choose ACH file to upload");
int returnVal = chooser.showOpenDialog(chooser);
if(returnVal == JFileChooser.APPROVE_OPTION)
{
try{ //Section for the buffer reader/writer.
String sCurrentLine;
br = new BufferedReader(new FileReader(chooser.getSelectedFile()));
bw = new BufferedWriter(new FileWriter(chooser.getCurrentDirectory()+"//NachaOutput.ACH"));
while((sCurrentLine = br.readLine()) !=null)
{
//Below is conditional statements that check to see if the line contains certain
//characters. If they do the it takes the lines and writes them to a new
//document (set above). It also adds +1 to the counter so the same numbers
//will not be written twice.
if (sCurrentLine.startsWith("5")){
five = sCurrentLine;
}else if (sCurrentLine.startsWith("6")){
list.add(sCurrentLine);
}else if (sCurrentLine.startsWith("8")){
eight = sCurrentLine;
}else{
}
}
while(list.size() > 0){
String six = null;
bw.write(five);
bw.newLine();
six = list.get(0);
bw.write(six);
bw.newLine();
list.remove(0);
bw.write(eight);
bw.newLine();
}
}catch (IOException e){
e.printStackTrace();
} finally {
try {
if (br != null)br.close();
if (bw != null)bw.close();
}catch (IOException ex){
ex.printStackTrace();
}
}
}
}
}
更新： 对于任何看过这个或有兴趣的人，我想我会更新我的最新进展。这次我必须编辑程序，以便它可以接受一个可能包含多个5或6的ACH文件，这意味着我需要程序循环遍历第一个5的实例，每6个循环后跟8，然后是下一个实例5然后是每6个后跟8个，依此类推。
我最终在“while”循环内部的“while”循环中使用了“if语句”。如果有人有办法更好地做到这一点或使代码更专业，我很乐意听到它：
package nacha;
import java.io.*;
import java.util.ArrayList;
import javax.accessibility.Accessible;
import javax.swing.JComponent;
import javax.swing.JFileChooser;
import javax.swing.JOptionPane;
import javax.swing.filechooser.FileNameExtensionFilter;
public class Nacha extends JComponent implements Accessible
{
public static void main(String args[])
{
ArrayList<String> listSix = new ArrayList<String>(); //List used to store the 6 starting numbers.
ArrayList<String> listFive = new ArrayList<String>(); //List used to store the 5 starting numbers.
String five = null; //String used to store 5 starting numbers
String eight = null; //String used to store 8 starting numbers.
BufferedReader br = null;
BufferedWriter bw = null;
//GUI stuff below for the input file
JFileChooser chooser = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter("ACH Files", "ach");
chooser.setFileFilter(filter);
chooser.setDialogTitle("Please choose ACH file to upload");
int returnVal = chooser.showOpenDialog(chooser);
if(returnVal == JFileChooser.APPROVE_OPTION)
{
try{
String sCurrentLine; //Sets the string for the line the Buffered Reader is currently reading.
//Below sets the location for the reader/writer actions.
br = new BufferedReader(new FileReader(chooser.getSelectedFile()));
bw = new BufferedWriter(new FileWriter(chooser.getCurrentDirectory()+"//NachaOutput.ACH"));
while((sCurrentLine = br.readLine()) !=null)
{
//Below are the conditional statements that check to see if the line begins with a certain
//character then either (1)writes the line to a string (2)writes the line into the array list
//or (3)does nothing and "ignores" the line.
if (sCurrentLine.startsWith("5")){
listFive.add(sCurrentLine);
}else if (sCurrentLine.startsWith("6")){
listSix.add(sCurrentLine);
}else if (sCurrentLine.startsWith("8")){
eight = sCurrentLine;
}else{
}
}
while(listFive.size() > 0){ //While there is some value in the "5" list.
five = listFive.get(0); //Make the string "five" equal to index 0 of the list.
ArrayList<String> listSixDuplicate = new ArrayList<String>(listSix); //Creates a duplicate of "six" list to manipulate.
while(listSixDuplicate.size() > 0){ //While there is some value in the "6" list.
bw.write(five);
bw.newLine();
bw.write(listSixDuplicate.get(0));// <------- Writes information in correct format to the outgoing file.
listSixDuplicate.remove(0);
bw.newLine();
bw.write(eight);
bw.newLine();
int size = listSixDuplicate.size(); //Creates a variable called "size" that is the size of "six".
if (size == 0) //If the size of the list "six" is empty..
listFive.remove(0); //Remove the value from index "0" of list "five".
//Loops back to beginning to see if list "five" has any more values.
}
}
//Lets the user know what the output file is named and where it has been saved.
JOptionPane.showMessageDialog(null, "Output file saved as NachaOutput.ach to " + chooser.getCurrentDirectory());
//Below is necessary exception handling for using the buffered reader/writer.
}catch (IOException e){
e.printStackTrace();
} finally {
try {
//Closes the buffer reader/writer.
if (br != null)br.close();
if (bw != null)bw.close();
}catch (IOException ex){
ex.printStackTrace();
}
}
}
}
}