Hadoop fileSystem.create 没有文件夹会自动创建吗

在Hadoop中，如果你使用FileSystem.create()方法来创建一个新的文件，如果该文件所在的目录不存在，该方法并不会自动创建目录。因此，在创建文件之前，你需要确保目录已经存在，或者使用FileSystem.mkdirs()方法来创建目录。如果目录已经存在，FileSystem.mkdirs()方法不会对现有目录做任何更改。

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org.apache.hadoop.fs.FileSystem

org.apache.hadoop.fs.FileSystem is a Java class in the Hadoop core library that provides a unified API to access and manage files and directories across different file systems. It abstracts the underlying file system implementation and provides a common interface for applications to work with files and directories.

FileSystem supports various file systems, such as HDFS, local file system, Amazon S3, and others. It provides methods for creating, deleting, renaming, and listing files and directories, as well as reading and writing data to files.

This class is an essential component of Hadoop's distributed file system, and it is widely used in Hadoop MapReduce and Hadoop Distributed File System (HDFS) applications. It also serves as a foundation for higher-level file system abstractions, such as Hadoop's FileContext API.

hadoop2.x和hadoop3.x的区别

Hadoop 2.x和Hadoop 3.x的区别主要在以下几个方面：

1. YARN的改进：Hadoop 2.x中引入了YARN（Yet Another Resource Negotiator），使得Hadoop可以支持多种计算框架，如MapReduce、Spark、Storm等。而Hadoop 3.x进一步改进了YARN，提高了其可伸缩性和容错性。

2. HDFS的改进：Hadoop 3.x中对HDFS进行了一系列改进，如增加了EC（Erasure Coding）编码、支持多个NameNode等，提高了其可靠性和性能。

3. 支持新的硬件架构：Hadoop 3.x支持新的硬件架构，如ARM处理器和NVMe SSD等，提高了Hadoop在这些硬件上的性能。

4. 其他改进：Hadoop 3.x还进行了一些其他的改进，如增加了容器化支持、改进了安全性等。