HashMap is very useful when a counter is required.
HashMap<String, Integer> countMap = new HashMap<String, Integer>(); //.... a lot of a's like the following if(countMap.keySet().contains(a)){ countMap.put(a, countMap.get(a)+1); }else{ countMap.put(a, 1); } |
In this post, I write a little bit about the basic ideas of web server, Servlet container and its relation with JVM. I want to show that Servlet container is nothing more than a Java program.
String is immutable in Java. An immutable class is simply a class whose instances cannot be modified. All information in an instance is initialized when the instance is created and the information can not be modified. There are many advantages of immutable classes. This article summarizes why String is designed to be immutable. This post illustrate the immutability concept in the perspective of memory, synchronization and data structures.
This post summarizes a commonly asked question about Java constructors.
When you write an article or something in text or in latex, you may want to spell check the content. Word is a very good tool, you may want to use it. However, it is not free, and you will need to pay. Actually you can use word online and do spell checking. The following … Read more
This article analyzes answers for a top-voted questions on Stack Overflow. The person who asked this question got a lot of reputation points, which could grant him permissions to do a lot of things on Stack Overflow. This does not make sense to me, but let’s take a look at the question first.
The question is “how to convert the following array to an ArrayList?”.
If you use eclipse, you probably format your code by pressing Ctrl+Shift+F or right clicking Source -> Format very often. This function is also provide in JDT, so you can also format your Java code in Java code.
Finding the correct JDT API for doing this job, however, is not straight-forward. In the following code, you will see one of the classes being used is actually an internal class.
This is the program every Java programmer knows. It is simple, but a simple start can lead to deep understanding of more complex concepts. In this post I will explore what can be learned from this simple program. Please leave your comments if hello world means more to you.
HelloWorld.java
public class HelloWorld { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub System.out.println("Hello World"); } } |
In Java, an array stores either primitive values (int, char, …) or references (a.k.a pointers) to objects.
When an object is created by using “new”, a memory space is allocated in the heap and a reference is returned. This is also true for arrays, since arrays are objects in Java.
