Top programming languages, August 2017

The top 20 programming languages ranking according to the TIOBE index
11 August

The TIOBE index is an index that estimates the popularity of programming languages based on the search engines queries results calculation containing the name of the language (a query of the form + "<language> programming").

Several of the most visited portals are used to collect information. Among them: Google, Blogger, Wikipedia, YouTube, Baidu, Yahoo !, Bing, Amazon. The index is calculated monthly.

On the August of 2017, according to TIOBE, top 3 programming languages are:

  1. Java
  2. C
  3. C++

 TIOBE index August 2017
TIOBE index August 2017

As you can see, Visual Basic .NET, Ruby, Swft, R, Go, MATLAB, Scratch and Dart had increased their popularity. For example, for a last year, GO gained 4 points (at 16 position now) and Dart burst on top 20 (now 20, year ago was at 26).

TIOBE Community Index August 2017
TIOBE Community Index August 2017

On the pic above, you can see the popularity of different programming languages from 2002 to 2017. Java, C and C++ are always in a trend. 

String concatenation implementation in Java 9

Guide on String concatenation implementation in Java 9 with code examples 
17 October

For a start, let's see how string concatenation was implemented in old versions. The "old" way output a bunch of StringBuilder-oriented operations. Let's check this code:

public class Example {
    public static void main(String[] args)
    {
        String result = args[0] + "-" + args[1] + "-" + args[2];
        System.out.println(result);
    }
}

If we compile that with JDK 8 or earlier and then use javap -c Example to see the bytecode, we see something like this:

public class Example {
  public Example();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class java/lang/StringBuilder
       3: dup
       4: invokespecial #3                  // Method java/lang/StringBuilder."<init>":()V
       7: aload_0
       8: iconst_0
       9: aaload
      10: invokevirtual #4                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      13: ldc           #5                  // String -
      15: invokevirtual #4                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      18: aload_0
      19: iconst_1
      20: aaload
      21: invokevirtual #4                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      24: ldc           #5                  // String -
      26: invokevirtual #4                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      29: aload_0
      30: iconst_2
      31: aaload
      32: invokevirtual #4                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      35: invokevirtual #6                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      38: astore_1
      39: getstatic     #7                  // Field java/lang/System.out:Ljava/io/PrintStream;
      42: aload_1
      43: invokevirtual #8                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
      46: return
}

As you can see, it creates a StringBuilder and uses append. This is famous fairly inefficient as the default capacity of the built-in buffer in StringBuilder is only 16 chars, and there's no way for the compiler to know to allocate more in advance, so it ends up having to reallocate. It's also a bunch of method calls. 

Let's look at what Java 9 generates:

public class Example {
  public Example();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public static void main(java.lang.String[]);
    Code:
       0: aload_0
       1: iconst_0
       2: aaload
       3: aload_0
       4: iconst_1
       5: aaload
       6: aload_0
       7: iconst_2
       8: aaload
       9: invokedynamic #2,  0              // InvokeDynamic #0:makeConcatWithConstants:(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
      14: astore_1
      15: getstatic     #3                  // Field java/lang/System.out:Ljava/io/PrintStream;
      18: aload_1
      19: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
      22: return
}

It makes a single call to makeConcatWithConstants from StringConcatFactory