8000 [RandomJava-101] add a Utility class to process file · fishercoder1534/RandomJava@5d53c4c · GitHub
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[RandomJava-101] add a Utility class to process file
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‎src/main/java/IO_example/ExtractFieldsFromFile.java

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package IO_example;
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import java.io.*;
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import java.util.HashSet;
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import java.util.Scanner;
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import java.util.Set;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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public class ExtractFieldsFromFile {
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private static final String BASE_FILE = "/Users/Downloads/base_file";
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private static final String UPDATE_FILE = "/Users/Downloads/update_file";
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public static void main(String... args) throws IOException {
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System.out.println("Program started.");
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readAllFieldNames("");
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Set<String> baseSet = readAllFieldNames(BASE_FILE);
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Set<String> updateFileSet = readAllFieldNames(UPDATE_FILE);
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Set<String> baseSetCopy = new HashSet<>(baseSet);
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baseSetCopy.removeAll(updateFileSet);
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System.out.println("baseSetCopy size after removing updateFileSet is: " + baseSetCopy.size());
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Set<String> linesOnlyExistInBaseSet = readLinesMatchingSet(BASE_FILE, baseSetCopy);
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// linesOnlyExistInBaseSet.forEach(System.out::println);
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System.out.println("Found a total of " + linesOnlyExistInBaseSet.size() + " matches.");
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appendLinesToFile(UPDATE_FILE, linesOnlyExistInBaseSet);
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System.out.println("Program finished.");
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}
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private static void appendLinesToFile(String updateFile, Set<String> linesToBeAppended) throws IOException {
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BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(updateFile, true));
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bufferedWriter.append("\n\n\n");
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bufferedWriter.append("#Added below fields from base file ---------\n");
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for (String str : linesToBeAppended) {
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bufferedWriter.append(str);
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bufferedWriter.append("\n");
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}
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bufferedWriter.close();
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}
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private static Set<String> readLinesMatchingSet(String filePath, Set<String> set) throws FileNotFoundException {
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if (filePath.isEmpty()) {
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System.out.println("No file to read, exit.");
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return null;
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}
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Scanner scanner = new Scanner(new File(filePath));
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scanner.useDelimiter("\n");
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Set<String> lines = new HashSet<>();
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int i = 0;
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while (scanner.hasNext()) {
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String line = scanner.next();
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i++;
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if (!line.isEmpty() && Character.isAlphabetic(line.charAt(0))) {
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String[] parts = line.split("=");
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if (set.contains(parts[0])) {
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lines.add(line);
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}
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}
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}
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scanner.close();
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System.out.println("A total of " + i + " lines were gone through, and found a total of " + lines.size() + " matches.");
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return lines;
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}
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public static Set<String> readAllFieldNames(String filePath) throws IOException {
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if (filePath.isEmpty()) {
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System.out.println("No file to read, exit.");
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return null;
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}
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Scanner scanner = new Scanner(new File(filePath));
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scanner.useDelimiter("\n");
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assertTrue(scanner.hasNext());
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int i = 0;
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int nonEmptyLines = 0;
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Set<String> fields = new HashSet<>();
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while (scanner.hasNext()) {
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String line = scanner.next();
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i++;
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if (!line.isEmpty() && Character.isAlphabetic(line.charAt(0))) {
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String[] parts = line.split("=");
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fields.add(parts[0]);
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nonEmptyLines++;
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}
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}
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System.out.println("For this file: " + filePath + ": A total of " + i + " lines, in which " + nonEmptyLines + " are non empty.");
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scanner.close();
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return fields;
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}
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}

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