Ben Chuanlong Du's Blog

It is never too late to learn.

Understand System.identityHashCode in Java

Tips and Traps

  1. You cannot get the address of an object in Java (without hacking). System.identityHashCode(obj) is the next best thing you can have. This trick (combined with the timestamp) is used to generate default seed for random number generators in Java.

Java IO

References

  1. Generally speaking, BufferedReader/BufferedWrite are preferred over InputStreamReader/InputStreamWriter.

https://docs.oracle.com/javase/8/docs/api/java/io/BufferedWriter.html

https://stackoverflow.com/questions/6976893/in-java-what-is-the-advantage-of-using-bufferedwriter-to-append-to-a-file

public static Stream\<String> java.nio.file.Files.lines

public static List\<String> java.nio.file.Files.readAllLines

Read all lines from a file. Bytes from the file are decoded into characters using the UTF-8 charset. Notice that this method returns a List of Strings, which is different from the method java.nio.file.Files.lines (who returns a Stream of Strings).

User in Docker

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

User switching in Docker

  1. USER some_user in Dockerfile, some_user has to exists
  2. su in Dockerfile or shell scripts
  3. docker run --user some_user

@pedrolucasoliva i am docker specialist i give you a …

Kotlin vs Scala

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

https://www.quora.com/Is-Kotlin-so-similar-to-Scala-What-are-the-differences/answer/Bruce-Richardson-4

Fix Xcrun Error in Mac

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

xcode-select --install

Reference

https://apple.stackexchange.com/questions/254380/why-am-i-getting-an-invalid-active-developer-path-when-attempting-to-use-git-a