Example 1:

server {
    listen 80;
    index index.html index.htm index.nginx-debian.html index.php;
    server_name aaa.bbb.ccc.ddd;
    location ~/app2(.*)$ {
        proxy_set_header X-Real-IP  $remote_addr;
        proxy_set_header X-Forwarded-For  $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_pass http://aaa.bbb.ccc.ddd:8001$1;
    }
}

ss comand

sudo ss -ltu
sudo ss -ltup  #show process

Only nested classes (inner classes) can be static.

Static methods can be overloaded but cannot be overrode.

1. String values are stored in String constant pool. It can be accessed by multiple client.
2. It is used by the class loading mechanism. For security reason, it should not be changed to other value.
3. Immutable string allow to cache its hashcode. It makes hashmap/hashtable very fast since they don’t calculate hashcode everytime.
4. String instance is thread-safe in Java.

Lambda expression replaces anonymous classes and removes all boiler plate, enabling you to write code in functional style, which is some time more readable and expression.

Lambda Expression vs Anonymous class

1. Keyword this. For anonymous class this keyword resolves to anonymous class, whereas for lambda expression this keyword resolves to enclosing class where lambda is written.
2. The compiled way. Java compiler compiles lambda expressions and convert them into private method of the class.

Sort in non-standard way

In python2

>>> a = ['floor', 'house', 'room', 'roof']
>>> a.sort(lambda x,y: cmp(len(x), len(y)))
>>> a
['room', 'roof', 'floor', 'house']
>>>

In Python3

>>> a = ['floor', 'house', 'room', 'roof']
>>> a.sort(key=lambda x: (len(x)))
>>> a
['room', 'roof', 'floor', 'house']
>>>

Closures - functions evaluated in an environment containing bound variables

In python2

>>> def comp(threshold):
...     return lambda x: x < threshold
...
>>> func_a = comp(10)
>>> func_b = comp(20)
>>> print func_a(5), func_a(9), func_a(15), func_a(25)
True True False False
>>> print func_b(5), func_b(9), func_b(15), func_b(25)
True True True False

In python3

>>> def comp(threshold):
...     return lambda x: x < threshold
...
>>> func_a = comp(10)
>>> func_b = comp(20)
>>> print(func_a(5), func_a(9), func_a(15), func_a(25))
True True False False
>>> print(func_b(5), func_b(9), func_b(15), func_b(25))
True True True False

Mapping - performs a function call on each element of a list.

In python2

>>> a = [1, 2, 3, 4, 5, 6]
>>> print map(lambda x: x*x, a)
[1, 4, 9, 16, 25, 36]

In python3

>>> a = [1, 2, 3, 4, 5, 6]
>>> [item for item in map(lambda x: x*x, a)]
[1, 4, 9, 16, 25, 36]

Filter - returns all elements from a list that evaluate True when passed to a certain function.

In python2

>>> a = [1, 2, 3, 4, 5, 6]
>>> filter(lambda x: x % 2 == 0, a)
[2, 4, 6]

In python3

>>> a = [1, 2, 3, 4, 5, 6]
>>> list(filter(lambda x: x % 2 == 0, a))
[2, 4, 6]

Reduce - The fold/reduce function runs over all elements in a list (usually left-to-right), accumulating a value as it goes.

>>> from functools import reduce
>>> a = [1, 2, 3, 4, 5, 6]
>>> reduce(lambda x, y: x+y, a)
21
>>>

This performs (((((1 + 2) + 3) + 4) + 5) + 6) = 21

Install pymongo

pip install pymongo

The OS module in Python provides functions to using operating system dependent functionality.
To use it, import the OS module “import os”

Solution on Ubuntu:
Using the following command and find with process is holding the dataset.

grep zroot/2013-10-15T065955229209 /proc/*/mounts

note: replace zroot/2013-10-15T065955229209 as your mount point.