point of sale and inventory system source code in java

, the following first describes the following types.Strong referencesThis is the most commonly used reference type, and when you execute the following statement, the variable is o a strong reference.Object o = new Object (); The object that the strong reference points to is not cleaned by the GC at any time. In general, for resident-class applications (such as server), the memory consumed tends to rise over time, and if the program uses strong references, it is easy to cause a memo

the custom class as a key value exists must do this, but not as a key value can choose not to do (but for the sake of specification, or to overwrite, So it becomes necessary). If you comment out the equals or hashcode in the test code, you will not get the correct result:public class PhoneNumber {private int areacode; private int prefix; private int linenumber; Public PhoneNumber (int areacode, int prefix, int linenumber) {this.areacode

The return value of Integer.bitcount (i) in Java is the number of 1 in the binary representation of I. The source code is as follows:public static int Bitcount (int. i) { //HD, figure 5-2 i = i-((i >>> 1) 0x55555555); i = (I 0x33333333) + ((I >>> 2) 0x33333333); i = (i + (i >>> 4)) 0x0f0f0f0f; i = i + (i >>> 8); i = i

Socke, also known as "socket", is used to describe IP addresses and ports. It is a communication chain handle. Applications usually send requests to or respond to network requests through "Sockets. Compile the socke server code: Package com. evan. blog; import java. io. IOException; import java. io. inputStream; import java.net. serverSocket; import java.net. so

Read the HashMap (1) and javahashmap of Java source code with me. Recently, I am very busy. I want to learn and discuss some Java source code and its implemented Data Structure with you, Not a high level of things. If you are inte

Method 1. find the JDK directory used in Eclipse: preferences... -> JAVA-> installed jres-> JVM 1.6.0 (MacOS X default ). 2. copy src.zip to/system/library/frameworks/JavaVM. framework/versions/1.6.0/home3. restart eclipse. method 2 default Mac machine JDK is without source code, need to download

This seat has previously published an articleArticle: Log cutting and cleaning tools implemented in Java are heavily reproduced on the Network (although most of them do not indicate the source of the original article ^_^ ). There are a lot of official comments to this seat, hoping to provide toolsSource code. Therefore, this seat does not dare to copy itself, and

com.luo.test;import com.luo.errorcode.LuoErrorCode;import com.luo.exception.BusinessException;publicclass ExceptionTest { publicstaticvoidmain(String args[]) { null; ifnull){ thrownew BusinessException(LuoErrorCode.NULL_OBJ); } }}Execution Result:Add: In our actual project, for example, someone else calls you interface. You may need to see if the object he passed is not empty, and first infer that the object passed is null for a friendly hint "[LUO001] obje

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For the Java Collection class, look at the two graphs firstThese two graphs roughly depict the Java Collection class overview, two systems, a collection set system, a map set system. Before talking about the collection class, say iterable this interface, this interface before jdk1.8, there is only one method iteratorde

don't need to modify it in general.HashMap is a data structure that supports fast access, and it is important to understand its data structure in order to understand its performance.Third, data structureWe know that the two most commonly used structures in Java are arrays and analog pointers (references), and almost all data structures can be combined using both, HashMap. In fact, HashMap is a "chain table hash", which is the following data structure

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-decimal conversion of the IP address of the computer network, it is often found255=2^7+2^7-1;2^7=2^6+2^5 ....... 2^1+2^0+12^k=2^ (k-1) +2^ (k-2) +............+2^1+2^0+1// This can be demonstrated by an iterative approach to 2^k= (*2^) k-1 (=2^) k-1 (+2^ )// with k-1 to replace K namely K=k-12^ (k-1) =2^ (k-2) +2^ (k-2) and so on there will be 2^k=2^ (k-1) +2^ (k-2) +............+2^1+2^1 that is, the original proof.What is the connection between this and the complement?If there is a positive a=f

Source code analysis: Memory Allocation of Java objects (1) Java objects are allocated in two ways: Fast allocation and slow allocation. The lock-free pointer collision technology is used to distribute the objects in the new generation Eden zone, the slow distribution has different invocation Layers Based on the imple

] = (byte) (W >>8) 255); BigInteger POW=NewBigInteger ("89126272330128007543578052027888001981",Ten); BigInteger MoD=NewBigInteger ("86f71688cdd2612ca117d1f54bdae029", -); BigInteger K0=NewBigInteger (Bkey); BigInteger K1=k0.modpow (POW, mod); String S0=integer.tostring (ID); String sz="0"; while(S0.length ()! =5) {S0=Sz.concat (S0); } S0= S0.concat ("-"); String S1=encodegroups (K1); S0=S0.concat (S1); returnS0; } Public Static voidMain (string[] args) {if(Args.length = =0) {System.err.print

Java concurrency series [7] ---- CountDownLatch source code analysis, CountDownLatch is a useful tool class. With it, we can intercept one or more threads so that they can be executed after a certain condition is ripe. It provides a counter internally. When constructing a lock, you must specify the initial value of the counter and the initial value of the counter

Java concurrent packet source code learning-AQS framework (2) CLH lock queue and spin lock, aqsclh As mentioned in the previous article, AQS is based onCLH lock queueSo what is CLH lock queue? complexity is complicated, simple, and simple. The so-called greatest truths are simple: CLH lock queue is actually a FIFO queue, and each node (thread) in the queue only n