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  When will resizing be triggered in Java HashMap?

HashMap is one of the most frequently used collection types in Java, it stores key-value pairs. Ideally it expects to use hash table which expects the data access time complexity to be O(1), however, due to hash conflicts, in reality, it uses linked list or red-black tree to store data which makes the worst case time complexity to be O(logn).  Although collections are using data structures like arrays and linked lists, unlike arrays, they will dynamically resize when there is not enough spa...

   JAVA,RESIZE,HASHMAP,THRESHOLD     2020-05-02 20:41:19

  Implementation of +,-,*,/ with bitwise operator

There is a question asked on Stackoverflow : Divide a number by 3 without using *,/,+,-,% operators. This question is an Oracle interview question. Some people give excellent answers. You can go there and take a look. Usually we need to use bitwise operators to do this kind of implementations. Here I want to show you ways to implement +,-,*,/ with bitwise operators. A bitwise operation operates on one or more bit patterns or binary numerals at the level of their individual bits. It is a fast, pr...

   Bitwise operator,Shift,Add,Subtract,Multiplication,Division     2012-08-05 01:52:47

  What does super.clone() do?

Object class has a protected clone() method declared to make it possible for all classes make a clone of itself when needed. The clone() is often used when a new instance of the class is needed while at the same time to maintain the same state as the original object. Any class which wants to have clone enabled has to implement the marker interface Cloneable. If a class which implements Cloneable doesn't override the Object.clone() method, the Object.clone() method will be called to just make a b...

   Cloneable,super.clone(),clone,Java     2015-01-07 05:25:52

  A HTTPS client and HTTPS server demo in Java

In this post, I will create a HTTPS server and HTTPS client demo which can establish HTTPS communication between a server and a client using Java. This should be very useful when we want to test our understanding about SSL communication. We will use both a detailed SSL client and a simple HttpsURLConnection as the HTTPS client. Before creating the actual HTTPS server and HTTPS client, we first need to generate the keystore and truststore to be used by the server and client. To generate the keyst...

   SSL,HTTPS,JAVA,DEMO     2015-10-23 09:04:36

  Different types of keystore in Java -- BKS

BKS is a keystore format provided by the popular third party Java cryptographic library provider -- BouncyCastle. It is a keystore similar to the JKS provided by Oracle JDK.  Before starting to use BKS, the BouncyCastle provider has to be downloaded and installed. To download the provider, please go to BouncyCastle download page. The provider can be installed by adding an entry in the java.security file. security.provider.N=org.bouncycastle.jce.provider.BouncyCastleProvider N means the pr...

   JAVA,KEYSTORE,BOUNCYCASTLE,BKS     2016-07-03 03:00:18

  Can API be copyrighted? At least Oracle hopes so

  The result of the lawsuit case war between Oracle and Google is clearer now. The court said that 9 lines of code of Android has violated intellectual property right, these 9 lines of code can be ignored relative to the number of codes for the whole Android system. But just like LinuxToy points out that the reasons why this case catches so much attention are : 1). The amount of money Oracle asked from Google is $1 billion; 2). The statement says Java language itself doesn't violate the int...

   Oracle,Google,API,Copyright,Lawsuit case     2012-05-11 00:47:58

  Use Memory Analyzer Tool in Eclipse

When developing applications, we often encounter memory issues of an application. To analyze how much memory each class takes, we need to have some specific tools to assist us. One of them is Memory Analyzer Tool on Eclipse. The Eclipse Memory Analyzer is a fast and feature-rich Java heap analyzer that helps you find memory leaks and reduce memory consumption. To use the Memory Analyzer Tool, you first need to install it on Eclipse. You can go to Help -> Install New Software.... Paste  h...

   Memory analyzer tool, Eclipse,heap dump, HPROF     2014-10-28 07:22:35

  Haxe: Another multiplatform language

There are two kinds of programmers: One is using different languages to solve problems, the other is inventing languages to solve problems. Haxe is an emerging open source programming language which is universal, powerful and easy-to-use. Some languages claimed they were multiplatform languages, such as Java, C# and ActionScript. They all are based on some platforms, Java has JVM, C# has .Net and ActionScript has Flash Player. While Haxe is a trule multiplatform language, it can be used to devel...

   Haxe,Multiplatform,Open source     2012-06-11 08:08:28

  Fastjson just fixed a bug which might cause out of memory issue

Fastjson just fixed a bug which might cause service down a few days ago. This bug is caused by some mishandling of special character \x which is an escaped character to indicate hexdecimal number. The impact of this bug would be big if the attacker constructs a malicious data which would cause the service down.  The code which causes the issue is in com.alibaba.fastjson.parser.JSONLexerBase#scanString, when a JSON string is passed in, fastjson would parse the string character by c...

   FASTJSON,ALIBABA,BUG,NEWS     2019-09-07 06:03:49

  Why 0.1+0.2 != 0.3

In programming languages such as JavaScript, c/c++, Java and Matlab, you will find that you will get unexpected result when doing float point calculation. For example, when calculating 0.1 + 0.1, you will not get 0.3: > 0.1 + 0.2 == 0.3 false > 0.1 + 0.2 0.30000000000000004 Don't be surprised of this result, this is the end result of IEEE 754 standard, float point number cannot be accurately represented according to IEEE 754 because: No enough memory is allocated for representing the num...

   float point,comparison,JavaScript     2014-11-19 05:32:46

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