You use these Java command-line parameters to help control the RAM use of application:

-Xmx to specify the maximum heap size
-Xms to specify the initial Java heap size

It means that javac.exe executable file, which exists in bin directory of JDK installation folder is not added to PATH environment variable. You need to add JAVA_HOME/bin folder in your machine's PATH to solve this error. You cannot compile and run Java program until your add Java into your system's PATH variable.

Add Path variable and you are good to go.

You need to get inside the container and then try to execute your command

Follow these steps:

1. Use docker ps to get the name of the existing container
2. Use the command docker exec -it /bin/bash to get a bash shell in the container
3. Or directly use docker exec -it to execute whatever command you specify in the container.

You can also use the following to delete the remote branch

**git push --delete origin serverfix**
Which does the same thing as

**git push origin :serverfix**
but it may be easier to remember.

A metaclass is the class of a class. A class defines how an instance of the class (i.e. an object) behaves while a metaclass defines how a class behaves. A class is an instance of a metaclass.

While in Python you can use arbitrary callables for metaclasses (like Jerub shows), the better approach is to make it an actual class itself. type is the usual metaclass in Python. type is itself a class, and it is its own type. You won't be able to recreate something like type purely in Python, but Python cheats a little. To create your own metaclass in Python you really just want to subclass type.

A metaclass is most commonly used as a class-factory. When you create an object by calling the class, Python creates a new class (when it executes the 'class' statement) by calling the metaclass. Combined with the normal __init__ and __new__ methods, metaclasses therefore allow you to do 'extra things' when creating a class, like registering the new class with some registry or replace the class with something else entirely.

When the class statement is executed, Python first executes the body of the class statement as a normal block of code. The resulting namespace (a dict) holds the attributes of the class-to-be. The metaclass is determined by looking at the baseclasses of the class-to-be (metaclasses are inherited), at the __metaclass__ attribute of the class-to-be (if any) or the __metaclass__ global variable. The metaclass is then called with the name, bases and attributes of the class to instantiate it.

However, metaclasses actually define the type of a class, not just a factory for it, so you can do much more with them. You can, for instance, define normal methods on the metaclass. These metaclass-methods are like classmethods in that they can be called on the class without an instance, but they are also not like classmethods in that they cannot be called on an instance of the class. type.__subclasses__() is an example of a method on the type metaclass. You can also define the normal 'magic' methods, like __add__, __iter__ and __getattr__, to implement or change how the class behaves.

Here's an aggregated example of the bits and pieces:
***
def make_hook(f):
"""Decorator to turn 'foo' method into '__foo__'"""
f.is_hook = 1
return f

class MyType(type):
def __new__(mcls, name, bases, attrs):

if name.startswith('None'):
return None

# Go over attributes and see if they should be renamed.
newattrs = {}
for attrname, attrvalue in attrs.iteritems():
if getattr(attrvalue, 'is_hook', 0):
newattrs['__%s__' % attrname] = attrvalue
else:
newattrs[attrname] = attrvalue

return super(MyType, mcls).__new__(mcls, name, bases, newattrs)

def __init__(self, name, bases, attrs):
super(MyType, self).__init__(name, bases, attrs)

# classregistry.register(self, self.interfaces)
print "Would register class %s now." % self

def __add__(self, other):
class AutoClass(self, other):
pass
return AutoClass
# Alternatively, to autogenerate the classname as well as the class:
# return type(self.__name__ + other.__name__, (self, other), {})

def unregister(self):
# classregistry.unregister(self)
print "Would unregister class %s now." % self

class MyObject:
__metaclass__ = MyType


class NoneSample(MyObject):
pass

# Will print "NoneType None"
print type(NoneSample), repr(NoneSample)

class Example(MyObject):
def __init__(self, value):
self.value = value
@make_hook
def add(self, other):
return self.__class__(self.value + other.value)

# Will unregister the class
Example.unregister()

inst = Example(10)
# Will fail with an AttributeError
#inst.unregister()

print inst + inst
class Sibling(MyObject):
pass

ExampleSibling = Example + Sibling
# ExampleSibling is now a subclass of both Example and Sibling (with no
# content of its own) although it will believe it's called 'AutoClass'
print ExampleSibling
print ExampleSibling.__mro__
***

It's a C trigraph. ??! is |, so ??!??! is the operator ||

Logarithmic running time (O(log n)) essentially means that the running time grows in proportion to the logarithm of the input size - as an example, if 10 items takes at most some amount of time x, and 100 items takes at most, say, 2x, and 10,000 items takes at most 4x, then it's looking like an O(log n) time complexity.

The numbers refer to the file descriptors (fd).

Zero is stdin
One is stdout
Two is stderr
2>&1 redirects fd 2 to 1.

This works for any number of file descriptors if the program uses them.

You can look at /usr/include/unistd.h if you forget them:
***
/* Standard file descriptors. */
#define STDIN_FILENO 0 /* Standard input. */
#define STDOUT_FILENO 1 /* Standard output. */
#define STDERR_FILENO 2 /* Standard error output. */
***
That said I have written C tools that use non-standard file descriptors for custom logging so you don't see it unless you redirect it to a file or something.

Sass was the first one, and the syntax is a bit different. For example, including a mixin:

***Sass: +mixinname()
Scss: @include mixinname()***
Sass ignores curly brackets and semicolons and lay on nesting, which I found more useful.

The key technical differences between an abstract class and an interface are:

Abstract classes can have constants, members, method stubs (methods without a body) and defined methods, whereas interfaces can only have constants and methods stubs.

Methods and members of an abstract class can be defined with any visibility, whereas all methods of an interface must be defined as public (they are defined public by default).

When inheriting an abstract class, a concrete child class must define the abstract methods, whereas an abstract class can extend another abstract class and abstract methods from the parent class don't have to be defined.

Similarly, an interface extending another interface is not responsible for implementing methods from the parent interface. This is because interfaces cannot define any implementation.

A child class can only extend a single class (abstract or concrete), whereas an interface can extend or a class can implement multiple other interfaces.

A child class can define abstract methods with the same or less restrictive visibility, whereas a class implementing an interface must define the methods with the exact same visibility (public).

he main difference is the scope difference, while let can be only available inside the scope it's declared, like in for loop, var can be accessed outside the loop for example. From the documentation in MDN (examples also from MDN):

let allows you to declare variables that are limited in scope to the block, statement, or expression on which it is used. This is unlike the var keyword, which defines a variable globally, or locally to an entire function regardless of block scope.

Variables declared by let have as their scope the block in which they are defined, as well as in any contained sub-blocks. In this way, let works very much like var. The main difference is that the scope of a var variable is the entire enclosing function:
***
function varTest() {
var x = 1;
if (true) {
var x = 2; // same variable!
console.log(x); // 2
}
console.log(x); // 2
}

function letTest() {
let x = 1;
if (true) {
let x = 2; // different variable
console.log(x); // 2
}
console.log(x); // 1
}`***
At the top level of programs and functions, let, unlike var, does not create a property on the global object. For example:
***
var x = 'global';
let y = 'global';
console.log(this.x); // "global"
console.log(this.y); // undefined***
When used inside a block, let limits the variable's scope to that block. Note the difference between var whose scope is inside the function where it is declared.
***
var a = 1;
var b = 2;

if (a === 1) {
var a = 11; // the scope is global
let b = 22; // the scope is inside the if-block

console.log(a); // 11
console.log(b); // 22
}

console.log(a); // 11
console.log(b); // 2***
Also don't forget it's ECMA6 feature, so it's not fully supported yet, so it's better always transpiles it to ECMA5 using Babel etc... for more info about visit babel website

To answer the part about when to use each function, use apply if you don't know the number of arguments you will be passing, or if they are already in an array or array-like object (like the arguments object to forward your own arguments. Use call otherwise, since there's no need to wrap the arguments in an array.
***
f.call(thisObject, a, b, c); // Fixed number of arguments

f.apply(thisObject, arguments); // Forward this function's arguments

var args = [];
while (...) {
args.push(some_value());
}
f.apply(thisObject, args); // Unknown number of arguments***
When I'm not passing any arguments (like your example), I prefer call since I'm calling the function. apply would imply you are applying the function to the (non-existent) arguments.

There shouldn't be any performance differences, except maybe if you use apply and wrap the arguments in an array (e.g. f.apply(thisObject, [a, b, c]) instead of f.call(thisObject, a, b, c)). I haven't tested it, so there could be differences, but it would be very browser specific. It's likely that call is faster if you don't already have the arguments in an array and apply is faster if you do.