data warehousing fundamentals

, andIP is 0800(System); ( 3 ) hardware address length and protocol length indicate the hardware address and the length of the High-level protocol address, so arp messages can be used on any hardware and any protocol network; ( 4 ) the Action field is used to denote the type of the message, arp request is 1 , arp response is 2 , rarp request is 3 , rarp response is 4 ; (5) The sender's hardware address (0-3 bytes): The first 3 bytes of the source host hardware address;(6) The sender's ha

ToString () method that can convert it to a string class.Sometimes we want to get a specific format for date, for example 20020324, we can use the following methods, first introduced in the file,ImportJava.text.SimpleDateFormat;ImportJava.util.*; java.util.Date Date=Newjava.util.Date ();//If you want to get the YYYYMMDD formatSimpleDateFormat sy1=NewSimpleDateFormat ("YyyyMMDD"); String DateFormat=Sy1.format (date);//If you want to get a separate year, month, daySimpleDateFormat Sy=NewSimpleDat

1. Encryption methodsymmetric encryption : encryption algorithm + passwordDES (56bits), 3des,aes (128bits), BlowfishCharacteristics:Encrypt, decrypt using the same passwordPartition the original text into a fixed-size block of data to encrypt the blocksDisadvantages:1. Password transmission2. Too many passwordsKey exchange: (IKE) DH algorithmUser authentication:Data integrity:Asymmetric encryption (public key cryptography): Key pair, the public key is

data types (auto-convert or cast), you can use wrapper classes for intermediate transitions. In general, a variable is declared first, then a corresponding wrapper class is generated, and the various methods of the wrapper class are used to convert the type.float f = 100.00fnew float (f); double D1 = F1.doublevalue (); 2. Conversion of strings to other data typesBy looking at the member methods provi

right sub-tree by the middle sequence. ③ post-order: Left and right root if the binary tree is non-empty, according to the post-secondary traversal of the left subtree, and then traverse the tree, and then access the root node. Two fork Tree Delete: ① no left no right: divided into: root node non-root node, but is the leaf node (divided into: Zuo right leaf) ② has left no right: divided into: root node non-root node (divided into: Left node right node) ③ There is no right left: divi

: 20172301: 20172304: Other (sentiment, thinking, etc., optional)ElseDo not listen to the sound of the forest dozen leaves, why not chant and Xu line.Learning progress BarLearning List lines of code (new/cumulative) Blog Volume (Add/accumulate) Learning Time (new/cumulative) Goal 5000 rows 30 Articles 400 hours First week 0/0 1/1 8/8 ResourcesReference

second word and capitalize the first letter4.java Data types1,. Basic data type: Divided into Boolean type (value is true or false), numeric typeNumeric type: Divided into integer type, floating-point typeInteger type: Byte (1 bytes (8 bits)), Short (2 bytes (16 bits), int (4 bytes (32 bits)), Long (8 bytes (64 bits)), char (2 bytes (16 bit))Floating-point types: single-precision float (4-byte (32-bit)), d

, so there are a lot of people who suggest using Angularjs, don't mix jquery. Of course, both have their pros and cons, and use whichever depends on their choice.The app in Ng is equivalent to a modular module that can define multiple controllers in each app, each with its own scope and without interfering with each other.Look at the HTML below:You will be pleasantly surprised to find that even without writing a line of JS code, you can finish computing and display the results in the interface.T

related information is often put together. A series of related variables are formed into a single entity, and this single entity type is called a structure. struct types are declared using the keyword struct.3. Enumeration typeAn enumeration type (also known as an enumeration) provides an efficient way to define a set of named integer constants that can be assigned to variables. Declares that an enumeration type begins with an enum. For example: Enum Weekday{sunday,monday,tuesday,wednesday,thur

, the number of bytes transferred is less than the number of bytes requested .Also note that in the Soketchannel implementation, Socketchannel only transmits the data that is prepared at this point (which may be less than count bytes). Therefore, Socketchannel may not transfer all of the requested data (count bytes) to FileChannel.(2) TransferTo ():The TransferTo () method transfers

1. Store the data in the collection into a text file case:Requirement: To store string data in the ArrayList collection into a text file?(1) Analysis:Through the meaning of the topic, we can know some of the following things,A string is stored in the ArrayList collection.Traverse the ArrayList collection to get the data.It is then stored in a text file.The text file description uses a character stream .(2)

Data type:The Java language is a strongly typed language that defines specific data types for each type of data, and allocates a different size of memory space in memoryClassification of data types:Basic data type:Integer:Number of bytes occupied

conversion rules: The sign bit will automatically expand, negative 1, positive 0.3. Automatic type conversion consists of the following:(1) byte->short->int->long->float->double(2) Data of int and char types can be converted to each other automatically in some cases.Error type for Java:Program errors are divided into compile-time syntax errors, run-time exception errors, and run-time logic errors.1. Compile-time syntax errors can easily locate errors

1. What are the types of reference data? Test analysis.Answer: There are two kinds.the first kind, Java provides us with good classes, such as the scanner class, the random class, etc., these existing classes contain a lot of methods and properties that we can use.Second, we create our own classes, according to the definition of the class, you can include multiple methods and properties in the class for us to use.2. The definition format of the classF

, the conversion is Nan, and any numeric value is compared to Nan, including Nan and Nan5. Logical operators and/And: requires both sides to be true|| Or: True on either side of the set！ Non: reverse the resulting valueTake a look at some of the following examples: var a=10,b=5,c=6; var x=a>bb>c; Console.log (x); //false var y=a console.log (y) //true Console.log ("T" "") //null Console.log ("T" "F") //f Console.log ((a-1) (b+=), b) //25,25 Console.log ((a-10)

+ is an operator that does the addition of data. The Boolean type cannot be converted to another type.Default conversionByte,short,char-int-long-float-doubleByte,short,char to each other, they participate in the operation first converted to the INT typeCasting (converting from a large data type to a small data type)Target type variable name = (target type) (

The floating-point literal defaults to a double type, so adding F or f;double type after the defined float data is not a suffix, but be sure to write D or x.x float in the decimal calculation The accuracy is not long and the number of significant digits (Mantissa) is short. The range of float is larger than the long index can be large. Floating-point numbers are imprecise and cannot be accurately compared to floating-point numbers.3) a character ty

1. Bufferedinputstream reading dataBufferedinputstream construction method, as follows: Construction Method Summary BufferedInputStream(InputStreamin)Create one BufferedInputStream and save its arguments, that is, the input stream for in future use. BufferedInputStream(InputStreamin, intsize)creates a specified buffer size BufferedInputStream and saves its arguments, that is, the input stream for in future use. 2. code example:1 Package

() substring () toLowerCase () toUpperCase () trim ()3. Building a StringStringBuilder high efficiency, suitable for single threadStringBuffer low efficiency, suitable for multi-threaded4.ScannerScanner (InputStream in) Scanner (new File ()) Scanner (String str)Nextline () line next () Word Nextint () nextdouble () Hasnext ()PrintWriter (file f) constructs a printwriter that writes to a fileFour, array1.array.copyof (oldarray,length) is often used for expansion, and arrays are allocated on the

odd pages even)//(divisible, returns the integer part of the quotient)Conditional operator: = = = = Assignment operator: = = = = *=/=%= **=//=Logical operators: And Or not (for example: not 1==1)Member operators: in Not IN (for example: if 1 in [1, 2, 3, 4])Identity operator: is isn't (for example: a=[1,2,3,4] If Type (a) is list:)Bitwise operators: (bitwise VS: AB) | (bitwise OR) ^ (bitwise XOR, XOR: Difference is 1, otherwise 0) ~ (bitwise Reversed) Ternary operators:A, B, C=1, 3, 5D=a if a>