用Java编写程序，进行文件夹增量备份。 程序功能与用法：指定源文件夹与目标文件夹，自动检测自上次备份以来源文件夹中内容的改变，包括修改的文件、新建的文件、新建的文件夹等等，自动复制新增或修改过的文件到目标文件夹中，自上次备份以来没有修改过的文件将被忽略而不复制，从而实现增量备份。

好的，这是一个文件夹增量备份的程序。以下是Java代码实现：

import java.io.*;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.text.SimpleDateFormat;
import java.util.*;

public class IncrementalBackup {

    private static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
    private static final String RECORD_FILE = "backup_record.txt";

    public static void main(String[] args) throws IOException {
        if (args.length != 2) {
            System.out.println("Usage: java IncrementalBackup [source folder] [destination folder]");
            return;
        }
        Path source = Paths.get(args[0]);
        Path destination = Paths.get(args[1]);
        Map<String, String> record = readRecord();
        Map<String, String> newRecord = new HashMap<>();
        Files.walkFileTree(source, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                String sourcePath = source.relativize(file).toString();
                String destinationPath = destination.resolve(sourcePath).toString();
                String lastModifiedTime = new SimpleDateFormat(DATE_FORMAT).format(new Date(attrs.lastModifiedTime().toMillis()));
                if (record.containsKey(sourcePath) && record.get(sourcePath).equals(lastModifiedTime)) {
                    System.out.println("Skip: " + sourcePath);
                    newRecord.put(sourcePath, lastModifiedTime);
                } else {
                    System.out.println("Copy: " + sourcePath);
                    Files.copy(file, Paths.get(destinationPath), StandardCopyOption.REPLACE_EXISTING);
                    newRecord.put(sourcePath, lastModifiedTime);
                }
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                String sourcePath = source.relativize(dir).toString();
                String destinationPath = destination.resolve(sourcePath).toString();
                if (!Files.exists(Paths.get(destinationPath))) {
                    System.out.println("Create directory: " + sourcePath);
                    Files.createDirectories(Paths.get(destinationPath));
                }
                return FileVisitResult.CONTINUE;
            }
        });
        writeRecord(newRecord);
    }

    private static Map<String, String> readRecord() throws IOException {
        Map<String, String> record = new HashMap<>();
        if (Files.exists(Paths.get(RECORD_FILE))) {
            try (Scanner scanner = new Scanner(new FileInputStream(RECORD_FILE))) {
                while (scanner.hasNextLine()) {
                    String line = scanner.nextLine();
                    String[] parts = line.split(" ");
                    if (parts.length == 2) {
                        record.put(parts[0], parts[1]);
                    }
                }
            }
        }
        return record;
    }

    private static void writeRecord(Map<String, String> record) throws IOException {
        try (PrintWriter writer = new PrintWriter(new FileOutputStream(RECORD_FILE))) {
            for (Map.Entry<String, String> entry : record.entrySet()) {
                writer.println(entry.getKey() + " " + entry.getValue());
            }
        }
    }
}

程序首先读取上一次备份的记录文件，然后遍历源文件夹中的所有文件和文件夹，对于每个文件，判断其是否修改过，如果是则进行复制，否则跳过。对于每个文件夹，如果目标文件夹中不存在，则创建。最后，将本次备份的记录写入记录文件中。

注意，该程序仅支持单层文件夹备份，如果需要备份多层文件夹，需要在遍历文件夹时进行递归调用。