Convert COBOL merge sort program to Java for MBA-18

merge_sort/MergeSortExample.java

@@ -0,0 +1,142 @@
+import java.io.*;
+import java.nio.file.*;
+import java.util.*;
+
+public class MergeSortExample {
+
+    static class CustomerRecord {
+        private int customerId;
+        private String lastName;
+        private String firstName;
+        private int contractId;
+        private String comment;
+
+        public CustomerRecord(int customerId, String lastName, String firstName, int contractId, String comment) {
+            this.customerId = customerId;
+            this.lastName = lastName;
+            this.firstName = firstName;
+            this.contractId = contractId;
+            this.comment = comment;
+        }
+
+        public int getCustomerId() { return customerId; }
+        public String getLastName() { return lastName; }
+        public String getFirstName() { return firstName; }
+        public int getContractId() { return contractId; }
+        public String getComment() { return comment; }
+
+        @Override
+        public String toString() {
+            return String.format("%05d%-50s%-50s%05d%-25s", 
+                customerId, 
+                padRight(lastName, 50),
+                padRight(firstName, 50),
+                contractId,
+                padRight(comment, 25));
+        }
+
+        public static CustomerRecord fromString(String line) {
+            if (line.length() < 135) {
+                throw new IllegalArgumentException("Invalid record length");
+            }
+            int customerId = Integer.parseInt(line.substring(0, 5));
+            String lastName = line.substring(5, 55).trim();
+            String firstName = line.substring(55, 105).trim();
+            int contractId = Integer.parseInt(line.substring(105, 110));
+            String comment = line.substring(110, 135).trim();
+            return new CustomerRecord(customerId, lastName, firstName, contractId, comment);
+        }
+    }
+
+    private static String padRight(String str, int length) {
+        return String.format("%-" + length + "s", str).substring(0, length);
+    }
+
+    public static void main(String[] args) {
+        try {
+            createTestData();
+            mergeAndDisplayFiles();
+            sortAndDisplayFile();
+            System.out.println("Done.");
+        } catch (IOException e) {
+            System.err.println("Error: " + e.getMessage());
+            System.exit(1);
+        }
+    }
+
+    private static void createTestData() throws IOException {
+        System.out.println("Creating test data files...");
+
+        List<CustomerRecord> eastRecords = Arrays.asList(
+            new CustomerRecord(1, "last-1", "first-1", 5423, "comment-1"),
+            new CustomerRecord(5, "last-5", "first-5", 12323, "comment-5"),
+            new CustomerRecord(10, "last-10", "first-10", 653, "comment-10"),
+            new CustomerRecord(50, "last-50", "first-50", 5050, "comment-50"),
+            new CustomerRecord(25, "last-25", "first-25", 7725, "comment-25"),
+            new CustomerRecord(75, "last-75", "first-75", 1175, "comment-75")
+        );
+
+        writeRecordsToFile("test-file-1.txt", eastRecords);
+
+        List<CustomerRecord> westRecords = Arrays.asList(
+            new CustomerRecord(999, "last-999", "first-999", 1610, "comment-99"),
+            new CustomerRecord(3, "last-03", "first-03", 3331, "comment-03"),
+            new CustomerRecord(30, "last-30", "first-30", 8765, "comment-30"),
+            new CustomerRecord(85, "last-85", "first-85", 4567, "comment-85"),
+            new CustomerRecord(24, "last-24", "first-24", 247, "comment-24")
+        );
+
+        writeRecordsToFile("test-file-2.txt", westRecords);
+    }
+
+    private static void mergeAndDisplayFiles() throws IOException {
+        System.out.println("Merging and sorting files...");
+
+        List<CustomerRecord> allRecords = new ArrayList<>();
+        allRecords.addAll(readRecordsFromFile("test-file-1.txt"));
+        allRecords.addAll(readRecordsFromFile("test-file-2.txt"));
+
+        allRecords.sort(Comparator.comparingInt(CustomerRecord::getCustomerId));
+
+        writeRecordsToFile("merge-output.txt", allRecords);
+
+        for (CustomerRecord record : allRecords) {
+            System.out.println(record);
+        }
+    }
+
+    private static void sortAndDisplayFile() throws IOException {
+        System.out.println("Sorting merged file on descending contract id....");
+
+        List<CustomerRecord> records = readRecordsFromFile("merge-output.txt");
+
+        records.sort(Comparator.comparingInt(CustomerRecord::getContractId).reversed());
+
+        writeRecordsToFile("sorted-contract-id.txt", records);
+
+        for (CustomerRecord record : records) {
+            System.out.println(record);
+        }
+    }
+
+    private static void writeRecordsToFile(String filename, List<CustomerRecord> records) throws IOException {
+        try (PrintWriter writer = new PrintWriter(new FileWriter(filename))) {
+            for (CustomerRecord record : records) {
+                writer.println(record.toString());
+            }
+        }
+    }
+
+    private static List<CustomerRecord> readRecordsFromFile(String filename) throws IOException {
+        List<CustomerRecord> records = new ArrayList<>();
+        try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                if (!line.trim().isEmpty()) {
+                    records.add(CustomerRecord.fromString(line));
+                }
+            }
+        }
+        return records;
+    }
+}