java coding basics

Interface: Public interface class name () {} There can only be abstract methods, common methods and construction methods do not exist Cannot create object property must be constant (static final) What is the use of interfaces and abstract classes? The role of interfaces and abstract classes is used when the parent class is inherited, and the abstract method is used to instruct the subclass to rewrite (implement) the K

the sine/cosine/tangent of a double type argumentTodegrees ()/toradians (): Return angle/radiansRandom (): Returns the stochastic numbertwo , Character class:　　The Character class is used to manipulate a single character, and the Character class wraps the value of a primitive type char in an object:CharCH ='a';//Unicode Character RepresentationCharUnichar ='\u039a'; //character ArrayChar[] Chararray ={'a','b','C','D','e'};The wrapper class character class is provided for the built-in data type

;Note: The difference between the float type and the double type, as well as the char type and the String type, has a related summary in the wiki, the small partners can go to see Oh ~ ~string is a common reference data type that is used to represent a string. In the development of programs, many operations are done using strings, such as user names, passwords, e-mail addresses, etc. in the system.PS: Other small partners on reference types will be detailed in the later course.Code:public class

Java basics-multithreading-② multithreading security issues, java What is thread security? Previous Java basics-multithreading-① thread creation and startup we will use the Runnable interface to create a thread, and multiple threads can share resources: 1 class Dog implement

spending, resulting in insufficient balance of the case of the deduction of money)Workaround: Add a synchronization method with the synchronized keywordFor example private synchronized void Makewithdrawal (int amount) {}Description: Each object is a lock with only one key per lock. Usually the object is not locked, only to see the synchronized synchronized method will be locked, the goal of synchronization is to protect important data, the actual lock is the method of accessing data. The key wi

; InputStream input =Null; OutputStream output =Null;while ((entry = Zipinput.getnextentry ())! =Null{System.out.println ("unzip" + entry.getname () + "file")); OutFile =New File (Outzippath + file.separator + entry.getname ()); if (! Outfile.getparentfile (). exists ()) {Outfile.getparentfile (). mkdir (); if (! Outfile.exists ()) {outfile.createnewfile ();} input = Zipfile.getinputstream (entry); output = new FileOutputStream (OutFile); int temp = 0; While (temp = Input.read ())! =-1) {outp

[Java Basics] several simple call relationships and methods, and several java-based calls Run the Code directly. 1 class lesson4AB 2 // public modifier method A under the same class, B can call each other 3 {4 public void A () 5 {6 B (); // equivalent to this. B (); 7} 8 public void B () 9 {10 A (); // equivalent to this. A (); 11} 12} 13 class lesson4C14 // The

Java basics-output stream-outputs string arrays to text files and java output streams Introduction: Example: Import java. io. fileInputStream; import java. io. fileOutputStream;/*** @ author czchina **/public class TestStream {public static void main (String [] args) {// TOD

Understanding Java IdentifiersQ: Is the identifier God horse?A: Identifiers are symbols that are used to name variables, classes, methods, and so on in a Java program.650) this.width=650; "src=" http://img.mukewang.com/5358910f00018c2c07320199.jpg "/>There are several rules to follow when using identifiers:1. Identifiers can consist of letters, numbers, underscores (_), dollar symbols ($) , but cannot conta

method is void, the return value cannot be used in the method!650) this.width=650; "style=" width:340px; src= "Http://img.mukewang.com/537d6fa40001bb3205080103.jpg"/>2. The return value of a method can have at most one and cannot return multiple values650) this.width=650; "style=" width:340px; src= "Http://img.mukewang.com/537d6fc800017bda05350165.jpg"/>3, the type of the method return value must be compatible, for example, if the return value type is int, you cannot return a String value650) t

Java basics-conversion between basic types and packaging classes, between basic types and strings, and between java stringsConversion between the basic type and the packaging class The conversion between the basic type and the packaging class is often required. Take Integer as an example (the operations of other packaging classes are the same ): After the automa