I'd actually recommend going here: https://github.com/JesusFreke/smali

It provides BAKSMALI, which is a most excellent reverse-engineering tool for DEX files. It's made by JesusFreke, the guy who created the fameous ROMs for Android.

Since Dheeraj Bhaskar's answer is relatively old as many years past.

Here is my latest (2019 year) answer:

Main Logic

from dex to java sourcecode, currently has two kind of solution:

• One Step: directly convert dex to java sourcecode
• Two Step: first convert dex to jar, second convert jar to java sourcecode

One step solution: dex directly to java sourcecode

Tools

• jadx

Process

1. download jadx-0.9.0.zip, unzip it, in bin folder can see command line jadx or GUI version jadx-gui, double click to run GUI version: jadx-gui

2. open dex file

then can show java source code:

3. File -> save as gradle project

then got java sourcecode:

Two Step solution

Step1: dex to jar

Tools

• dex2jar

Process

download dex2jar zip, unzip got d2j-dex2jar.sh, then:

• apk to jar: sh d2j-dex2jar.sh -f ~/path/to/apk_to_decompile.apk
• dex to jar: sh d2j-dex2jar.sh -f ~/path/to/dex_to_decompile.dex

example:

➜  v3.4.8 /Users/crifan/dev/dev_tool/android/reverse_engineering/dex-tools/dex-tools-2.1-SNAPSHOT/d2j-dex2jar.sh -f com.huili.readingclub8825612.dex
dex2jar com.huili.readingclub8825612.dex -> ./com.huili.readingclub8825612-dex2jar.jar
➜  v3.4.8 ll
-rw-------  1 crifan  staff   9.5M  3 21 10:00 com.huili.readingclub8825612-dex2jar.jar
-rw-------  1 crifan  staff   8.4M  3 19 14:04 com.huili.readingclub8825612.dex

Step2: jar to java sourcecode

Tools

• jd-gui: most popular, but many code will decompile error
• CRF: popular, minor code will decompile error
• Procyon: popular, no code decompile error
  • GUI tool based on Procyon
    • Luyten:
    • Bytecode Viewer
• others
  • Krakatau
  • Fernflower
  • old one: AndroChef
  • etc.

Process

here demo Procyon convert jar to java source code:

download procyon-decompiler-0.5.34.jar

then using syntax:

java -jar /path/to/procyon-decompiler-0.5.34.jar -jar your_to_decompile.jar -o outputFolderName

example:

java -jar /Users/crifan/dev/dev_tool/android/reverse_engineering/Procyon/procyon-decompiler-0.5.34.jar -jar com.huili.readingclub8825612-dex2jar.jar -o com.huili.readingclub8825612

using editor VSCode to open exported source code, look like this:

Conclusion

Conversion correctness : Jadx > Procyon > CRF > JD-GUI

Recommend use: (One step solution's) Jadx

for more detailed explanation, please refer my online Chinese ebook: 安卓应用的安全和破解

I have used

1. dex2jar + jd-gui
2. javadecompilers.com
3. enjarify
4. Apktool

But none beats google's own tools

1)Android Studio 2.x: build> analyze apk

2)Android Studio 3.0: Profile or Debug APK