Java

Hierarchy of Java Collection framework

Java Map Hierarchy

Thread Unsafe	Thread Safe
StringBuilder	StringBuffer
ArrayList	Vector
HashMap (allow key or value is null)	HashTable (key and value are nullable)
	Properties
TreeMap (red black tree)
	java.util.concurrent.*

The java.io package

线程生命周期图.png

线程死亡后，不能重新开启，再次开启是一个新的线程。

console.log("Hello world!");

print('Hello world!')

puts 'Hello world!'