Method Chaining

[tweet-dzone]Method chaining is a simple programming technique that can be implemented in almost any programming language. In simple words, it means that a method performs some operations on “this” object and then returns it so it can be used further more. It allows us to invoke several methods one after another, on one or different objects, usually written in the same line.

For example we can build a rectangle class using using the Method Chaining for setters. You can see the setters are a little bit different than regular setters:

class ChainedRectangle
    protected int x;
    public ChainedRectangle setX(int x) { this.x = x; return this; }

    protected int y;
    public ChainedRectangle setY(int y) { this.y = y; return this; }

    protected int width;
    public ChainedRectangle setWidth(int width) { this.width = width; return this; }

    protected int height;
    public ChainedRectangle setHeight(int height) { this.height = height; return this; }

    protected String color;
    public ChainedRectangle setColor(String color) { this.color = color; return this; }

Then if we need to build a rectangle we can write a single line for setting all the required values:

new         Rectangle().setX(10).setY(10).setWidth(13).setHeight(15).setColor("red");

Along with autocomplete option in most of todays IDEs method chaining might provide a suggestive way of doing some actions in less code.
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A few thoughts about memory cache

I was starting today to look on different approaches and techniques that are used in scalable web or non web applications. One technique used in many large systems is simply called “memory cache”. It means that data are cached in memory so the data will not be queried again.

Cache and memory cache exists for a long time; even the hardware parts link hard disks cd units have some sort of memory cache.

Why memory cache becomes so important when we talk about web applications? It’s simple. Because web applications happens to fulfill thousands of requests simultaneously. Or sometimes they have to. It’s obvious that keeping the data into memory and reuse it the next time you need it it will improve the performance. And it looks very simple. At the first view simple hashmap would do the job, unless…

There a few facts we need to be consider in real world:

  • What happens when the database is updated?
  • In most cases a web application create a thread for each http request. The same thing happens in java of php or other languages. The creation of the threads is handled by the web server, web container, and not by the code we write.
  • The scalable applications run distributed on multiple servers. If one application change the database, the cache system should be informed on all the machines.

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