HashMap 混乱。 Reading/Writing 到文件。 Java
HashMap confusion. Reading/Writing to files. Java
到目前为止的代码：
public class test1 {
public static void main(String[] args) throws IOException {
//declare reader and writer
BufferedReader reader = null;
PrintWriter writer = null;
//hash maps to store the data
HashMap<String, String> names = new HashMap<String, String>();
//read the first file and store the data
reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("IRStudents.txt"))));
String line;
String[] arg;
while ((line = reader.readLine()) != null) {
if (!line.startsWith("-")) {
arg = line.split(" ");
names.put(arg[0], arg[1]);
}
}
reader.close();
//read the second file, merge the data and output the data to the out file
writer = new PrintWriter(new FileOutputStream(new File("File_2.txt")));
reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("Marks.txt"))));
while((line = reader.readLine()) != null){
arg = line.split(" ");
writer.println(arg[0] + " " + names.get(arg[0]));
writer.println("Marks: " + arg[1]);
writer.println("- - - - - -");
}
writer.flush();
writer.close();
reader.close();
}
}
因此文本文件中的输出如下所示：
25220 Fiona
Marks: 68.3
- - - - - -
25212 Greg
Marks: 70.5
- - - - - -
我有另一个文本文件，其中包含另一组标记，其布局与第一个标记文件相同。
现在我想向数据集添加一组新标记所以它应该如下所示：
25220 Fiona
Marks: 68.3 Marks2: 21.2
- - - - - -
25212 Greg
Marks: 70.5 Marks2: 23.43
- - - - - -
那我能做些什么来补充呢？我假设我必须为新的文本文档添加一个新的哈希图？但是当我尝试做所有这些时，它从来没有完全奏效。
IR 学生：
25987 Alan
25954 Betty
25654 Chris
25622 David
添加新标记时，使用此方法将它们添加到现有标记中：
String key = arg[0];
String secondMarks = arg[1];
String theMarks = names.get(key);
theMarks = theMarks + " Marks2: " + secondMarks;
names.put(key, theMarks);
我想我理解你的问题，如果这不正确请告诉我。
要求是将此人收到的所有标记都放在自己的行上...
System.out 流中有两个打印函数。
打印和 println
arg = line.split(" ");
writer.println(arg[0] + " " + names.get(arg[0]));
writer.print("Marks: " + arg[1]);
for(int i = 2; i < args.length; i++){
writer.println(" Marks" + i + ": " + arg[i]);
}
writer.println("\n- - - - - -");
我认为您对字符串的操作太多了。如果您将有更多标记的文件以类似方式处理，则字符串操作可能会增加，这可能会降低您的代码的可读性，并可能为错误提供更多空间。我认为以下是更好的方法。
您可以创建具有以下结构的 MarksRecord class。
public class MarksRecord {
private String subject; // or whatever this variable name should be.
// in your case it should hold value marks1.
private double marks;
}
同样，您可以创建一个不可变的 Student/similar class，如下所示。这可能是一个值 class，它具有基于您在每个文件中读取的第一个数字的 equals 和 hashCode 方法。我猜是卷号或类似的东西可以以独特的方式识别学生。
public final class Student {
private final String rollNumber;
private final String name;
// equals, hashCode, and other methods.
}
然后在你的主要方法中你可以有一个
Map<Student, ArrayList<MarksRecord>>
。或者你也可以使用
Map<String, ArrayList<MarksRecord>>
其中第一个字符串是学生记录的卷号。
这样每次您有一个新的标记文件时，您的数据结构就能够容纳它。
您也可以执行以下操作。
package toBeDeleted;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
public class MarksProcessor {
private final Map<String, Record> map = new HashMap<>();
public static void main(String[] args) {
String fileName = "file1.txt"; // change it to your specific file.
MarksProcessor marksProcessor = new MarksProcessor();
marksProcessor.processFile(fileName, 0);
fileName = "file2.txt";
marksProcessor.processFile(fileName, 1);
marksProcessor.writeData();
}
private void processFile(String fileName, int marksIndex) {
try(/*specify your reader resources here*/) {
// read the first record and get rollNumber, name and marks.
String roll = "valueYouGot";
double value = 0.0; // the value you read.
Record record = map.get(roll);
// if record is null, you need to create one
// and put it into the map.
//record.updateMarks(marksndex, value);
}
}
private void writeData() {
// if this needs to be written to a file/stream, create a writer.
for (Map.Entry<String, Record> entry : map.entrySet()) {
String roll = entry.getKey();
Record record = entry.getValue();
if (record != null) {
String name = record.getName();
double marks1 = record.getMarks(0);
double marks2 = record.getMarks(1);
// Now you have all the values. Print them
// however you like. Wherever you like.
}
}
}
static class Record {
private String name;
private double[] marks = new double[2];
Record(String name) {
this.name = name;
}
public String getName() {
return name;
}
public double getMarks(int index) {
if (index < 0 || index > 1)
throw new IllegalArgumentException("index should be 0 or 1 but"
+ " the supplied index was " + index);
return marks[index];
}
public void updateMarks(int index, double value ) {
if (index < 0 || index > 1)
throw new IllegalArgumentException("index should be 0 or 1 but"
+ " the supplied index was " + index);
marks[index] = value;
}
@Override
public String toString() {
return "the way you want to type your output";
}
}
}
到目前为止的代码：
public class test1 {
public static void main(String[] args) throws IOException {
//declare reader and writer
BufferedReader reader = null;
PrintWriter writer = null;
//hash maps to store the data
HashMap<String, String> names = new HashMap<String, String>();
//read the first file and store the data
reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("IRStudents.txt"))));
String line;
String[] arg;
while ((line = reader.readLine()) != null) {
if (!line.startsWith("-")) {
arg = line.split(" ");
names.put(arg[0], arg[1]);
}
}
reader.close();
//read the second file, merge the data and output the data to the out file
writer = new PrintWriter(new FileOutputStream(new File("File_2.txt")));
reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("Marks.txt"))));
while((line = reader.readLine()) != null){
arg = line.split(" ");
writer.println(arg[0] + " " + names.get(arg[0]));
writer.println("Marks: " + arg[1]);
writer.println("- - - - - -");
}
writer.flush();
writer.close();
reader.close();
}
}
因此文本文件中的输出如下所示：
25220 Fiona
Marks: 68.3
- - - - - -
25212 Greg
Marks: 70.5
- - - - - -
我有另一个文本文件，其中包含另一组标记，其布局与第一个标记文件相同。
现在我想向数据集添加一组新标记所以它应该如下所示：
25220 Fiona
Marks: 68.3 Marks2: 21.2
- - - - - -
25212 Greg
Marks: 70.5 Marks2: 23.43
- - - - - -
那我能做些什么来补充呢？我假设我必须为新的文本文档添加一个新的哈希图？但是当我尝试做所有这些时，它从来没有完全奏效。
IR 学生：
25987 Alan
25954 Betty
25654 Chris
25622 David
添加新标记时，使用此方法将它们添加到现有标记中：
String key = arg[0];
String secondMarks = arg[1];
String theMarks = names.get(key);
theMarks = theMarks + " Marks2: " + secondMarks;
names.put(key, theMarks);
我想我理解你的问题，如果这不正确请告诉我。
要求是将此人收到的所有标记都放在自己的行上...
System.out 流中有两个打印函数。
打印和 println
arg = line.split(" ");
writer.println(arg[0] + " " + names.get(arg[0]));
writer.print("Marks: " + arg[1]);
for(int i = 2; i < args.length; i++){
writer.println(" Marks" + i + ": " + arg[i]);
}
writer.println("\n- - - - - -");
我认为您对字符串的操作太多了。如果您将有更多标记的文件以类似方式处理，则字符串操作可能会增加，这可能会降低您的代码的可读性，并可能为错误提供更多空间。我认为以下是更好的方法。
您可以创建具有以下结构的 MarksRecord class。
public class MarksRecord {
private String subject; // or whatever this variable name should be.
// in your case it should hold value marks1.
private double marks;
}
同样，您可以创建一个不可变的 Student/similar class，如下所示。这可能是一个值 class，它具有基于您在每个文件中读取的第一个数字的 equals 和 hashCode 方法。我猜是卷号或类似的东西可以以独特的方式识别学生。
public final class Student {
private final String rollNumber;
private final String name;
// equals, hashCode, and other methods.
}
然后在你的主要方法中你可以有一个
Map<Student, ArrayList<MarksRecord>>
。或者你也可以使用
Map<String, ArrayList<MarksRecord>>
其中第一个字符串是学生记录的卷号。
这样每次您有一个新的标记文件时，您的数据结构就能够容纳它。
您也可以执行以下操作。
package toBeDeleted;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
public class MarksProcessor {
private final Map<String, Record> map = new HashMap<>();
public static void main(String[] args) {
String fileName = "file1.txt"; // change it to your specific file.
MarksProcessor marksProcessor = new MarksProcessor();
marksProcessor.processFile(fileName, 0);
fileName = "file2.txt";
marksProcessor.processFile(fileName, 1);
marksProcessor.writeData();
}
private void processFile(String fileName, int marksIndex) {
try(/*specify your reader resources here*/) {
// read the first record and get rollNumber, name and marks.
String roll = "valueYouGot";
double value = 0.0; // the value you read.
Record record = map.get(roll);
// if record is null, you need to create one
// and put it into the map.
//record.updateMarks(marksndex, value);
}
}
private void writeData() {
// if this needs to be written to a file/stream, create a writer.
for (Map.Entry<String, Record> entry : map.entrySet()) {
String roll = entry.getKey();
Record record = entry.getValue();
if (record != null) {
String name = record.getName();
double marks1 = record.getMarks(0);
double marks2 = record.getMarks(1);
// Now you have all the values. Print them
// however you like. Wherever you like.
}
}
}
static class Record {
private String name;
private double[] marks = new double[2];
Record(String name) {
this.name = name;
}
public String getName() {
return name;
}
public double getMarks(int index) {
if (index < 0 || index > 1)
throw new IllegalArgumentException("index should be 0 or 1 but"
+ " the supplied index was " + index);
return marks[index];
}
public void updateMarks(int index, double value ) {
if (index < 0 || index > 1)
throw new IllegalArgumentException("index should be 0 or 1 but"
+ " the supplied index was " + index);
marks[index] = value;
}
@Override
public String toString() {
return "the way you want to type your output";
}
}
}