fundamentals of electrodynamics

Back to our game today, we add conditional judgment statements to our game and enrich gameplayOur previous code:Print ("---------Welcome to the place to guess the numbers, start---------") #输出提示guess =int (Input ("* Number range 0-100, enter the number you guessed:")) #读取输入, and then assign print (guess) # Print inputThe above is our previous code, relatively simple, just print the number you entered, forget it.We're in there today to add conditional judgments that make the game rich dot1. First

class. For objects associated with soft references, only when the memory is lowThe JVM will not recycle the object. Therefore, this is a good way to solve the problem of oom, and this feature is well suited for caching: such as Web caching, image caching, and so on. 3). Weak references (WeakReference): Weak references are also used to describe non-required objects, and when the JVM is garbage collected, the objects associated with the weak references are reclaimed, regardless of sufficient mem

occurs. - Private Static Final LongSerialversionuid = 1L; + PrivateString name; A Private intAge ; at //static members belong to a class and cannot be serialized. - Private Static intcount; - //transients cannot be serialized either. - transient Private intkey; - - Person () { inSYSTEM.OUT.PRINTLN ("Null parameter constructor"); - } to PublicPerson (String name,intAge ) { +System.out.println ("Parametric constructor"); - This. Name =name; the

derives from C + +, but omits all the incomprehensible features in C + +, such as header files, pointers, structures, cells, operator overloads, virtual base classes, and so on.portability: written programs can be run without modification on Windows, MacOS, UNIX and other platforms to "write once, run everywhere."Object-oriented: Java is a fully object-oriented language.Explanatory: Java interprets Java code by running the Java interpreter on different platforms (Java has a corresponding interp

Len (s) Request length "A%s parrot"% kind String formatting expressions "A {0} parrot". Format (Kind) Method of String formatting S.find (' xxx ') Search S.rstrip () Remove spaces S.replace (' xxx ', ' xxx ') Replace S.endswith (' xxx ') End With XXX ' xxx '. Join (Strlist) Entry and exit separators S.encode (' latin-1 ') Chan

Static memory allocation and dynamic memory allocation in C + +:1. The static object is a variable with a name, we manipulate it directly, and the dynamic object is a variable with no NameWe manipulate it indirectly through pointers. (Static memory allocation is because when the source code is compiled, the compiler allocates memory space for the variable instead of allocating memory when the program executes, and dynamic memory allocation allocates memory when the program executes).2. The alloc

1. Statements are executed on a line-by-row basis, unless you do not writeIf the statement uses an if statement, his execution is jumping, and the IF statement is the process control2. Automatic boundary detection of blocks and statementsBecause Python does not have curly braces for these bounding symbols, it uses code indentation to control boundariesSimilarly, the end of a statement is not using semicolons, but also using code indentationIn the above example, for the indentation before the for

Object-oriented three features: encapsulation, inheritance, polymorphismThis section is the embodiment of object-oriented polymorphism1. Upward transformation of objectsThe upward transformation----assigns the object of the subclass to a reference to the parent class;Student s = new Student ();Person p = s;Or it can be writtenPerson p = new Student ();What members (variables and functions) can be called by a reference, depending on the data type of the applicationWhich method a reference invokes

(parameter) calls the constructor of the parent class ..... Ibid.Replication is also known as overwriting or rewriting1. Among the two classes that have a parent-child relationship2. The parent class and subclass each have a function, the definitions of the two functions (return value type, function name and parameter list) are identical5. Use super to call member functions in the parent classOverloading is in a class, the replication is in two classes, with Super call the parent class function

Reflection is of great significance in Java and is a dynamic mechanism for loading, detecting, and using classes that are completely unknown during compilation. In other words, a Java program can load a runtime to know the name of the class, learn its full construct (but not including the methods specific definition), and generate its object entities, or set values on its fields, or use its methods. Reflection is the basis of the framework, and the framework can greatly save the development cost

all the data in a curly brace, assigning an initial value to each element in the order in which the array is arranged.int a[3][4]={0,1,2,3,4,5,6,7,8,9,10,11};③ only assigns initial values to some elements.int a[3][4]={{1},{2},{4}};1 0 0 02 0 0 04 0 0 0int a[3][4]={{1},{0,2},{0,0,4}};1 0 0 00 2 0 00 0 4 0int a[3][4]={{1},{3,2}};1 0 0 03 2 0 00 0 0 0int a[3][4]={{1},{},{9}};1 0 0 00 0 0 09 0 0 0④ If an initial value is assigned to all elements, the first-dimension length can be unspecified when t

[] addr) creates inetaddress based on the host name and IP address provided. * Static inetaddress Getbyname (String host) determines the IP address of the host in the given host name. * * Obtained InetAddress class object, which encapsulates a non-static method to obtain the hostname and IP address **/inetaddress Ialocalhost=Inetaddress.getlocalhost (); System.out.println (Ialocalhost.tostring ()); System.out.println (Ialocalhost.gethostname ()); System.out.println

duplicate keys, and each key can be mapped to at most one value.3. What are the differences between the map collection and the collection collection?The map collection storage elements are paired, and the keys of the map collection are unique and the values are repeatable. This can be understood as: couplesThe collection collection storage element appears separately, and the collection son set is unique and the list is repeatable. This can be understood as: Bachelor (11.11)Attention:The data st

, Len); the } - Wuyi bos.close (); the bis.close (); - } Wu - // byte buffer stream reads and writes one byte at a time About Private Static voidMethod3 (file srcfile, file destfile)throwsIOException { $Bufferedinputstream bis =NewBufferedinputstream (NewFileInputStream ( - srcfile)); -Bufferedoutputstream BOS =NewBufferedoutputstream ( - NewFileOutputStream (DestFile)); A + intby = 0; the while(by = Bis.read ())! =-1) { - Bos.write (by); $

path, but pass a OutputStream object?A: The reason is simple, the byte buffer stream only provides buffers, designed for efficiency. However, the actual read and write operation is also dependent on the basic flow object implementation.3. Bufferedoutputstream Write Data , code example:1 Packagecn.itcast_05;2 3 ImportJava.io.BufferedOutputStream;4 ImportJava.io.FileOutputStream;5 Importjava.io.IOException;6 7 Public classBufferedoutputstreamdemo {8 Public Static voidMain (string[] args)th

1. FileInputStream reading data One byte array at a time byte[]Use FileInputStream to read one byte array at a time:int read (byte[] b)　　return value : The return value is actually the number of bytes actually read.2. code example:1 PackageCom.himi.fileinputstream;2 3 ImportJava.io.FileInputStream;4 Importjava.io.IOException;5 6 7 8 /**9 * Ten * Use FileInputStream one byte array at a time: int read (byte[] b) One * Return value: The return value is actually the number of bytes actually read A

1. Requirements: Copy the D:\\english.mp4 to the current project directory Copy.mp4code example:1 Packagecom.himi.filecopy;2 3 ImportJava.io.FileInputStream;4 ImportJava.io.FileOutputStream;5 Importjava.io.IOException;6 7 /**8 * 9 * Requirements: Copy the D:\\english.mp4 to the current project directory Copy.mp4Ten * One */ A Public classCOPYMP4 { - - Public Static voidMain (string[] args)throwsIOException { the //Data Source -FileInputStream FIS =NewFileInputStream ("D:\\engl

development use when we are developing, we will see abstract classes, or interfaces as parameters. And this time, we know that what is actually needed is a subclass object. If the method is called only once, we can use the format of the anonymous inner class to simplify. Interface Person {public abstract void study (); } class Persondemo {public void method (person p) {p.study (); }} class Persontest {public static void main (string[] args) {Persondemo

numbers C: Get the maximum value in three numbers (nesting of If statements) D: According to the score output corresponding to the class E: According to the month, the output corresponding to the season F: According to the x to calculate the corresponding Y value and output (4) Ternary operator F statement the second format of the relationship all ternary operators can be implemented, the if statement of the second format can be achieved. Conversely, it is not established. If the statement bod

is as follows:1 Packagecn.itcast_03;2 3 ImportJava.io.FileWriter;4 Importjava.io.IOException;5 ImportJava.io.PrintWriter;6 7 /*8 * 1: Any type of data can be manipulated. 9 * PRINT ()Ten * println () One * 2: Start auto Refresh A * PrintWriter pw = new PrintWriter (New FileWriter ("Pw2.txt"), true); - * or you should call the println () method to - * This time not only automatically refreshed , but also to achieve the data line-breaking . the * - * println () - * actually equivalent to :