定义函数学习1

public interface FunctionWithException<T, R, E extends Throwable> {

    /**
     * Calls this function.
     *
     * @param value The argument to the function.
     * @return The result of thus supplier.
     * @throws E This function may throw an exception.
     */
    R apply(T value) throws E;
}

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2024.10.20 最佳开源项目🔝:googleapis - 知乎 (zhihu.com)

使用

private FileSystem getFileSystem(
        org.apache.hadoop.fs.Path path,
        FunctionWithException<org.apache.hadoop.fs.Path, FileSystem, IOException> creator)
        throws IOException {
    if (fsMap == null) {
        synchronized (this) {
            if (fsMap == null) {
                fsMap = new ConcurrentHashMap<>();
            }
        }
    }

    Map<Pair<String, String>, FileSystem> map = fsMap;

    URI uri = path.toUri();
    String scheme = uri.getScheme();
    String authority = uri.getAuthority();
    Pair<String, String> key = Pair.of(scheme, authority);
    FileSystem fs = map.get(key);
    if (fs == null) {
        fs = creator.apply(path);
        map.put(key, fs);
    }
    return fs;
}

集合中验证重复出现的数据

final Set<String> duplicates =
        fieldNames.stream()
                .filter(n -> Collections.frequency(fieldNames, n) > 1)
                .collect(Collectors.toSet());