Convert android code to java code

How to Convert Kotlin Code to Java Code in Android Studio?

Java programming language is the oldest and most preferred language for Android app development. However, during Google I/O 2017, Kotlin has been declared as an official language for Android development by the Google Android Team. Kotlin has gained popularity among developers very quickly because of its similarities as well as interoperable with the Java language. One can mix code of Java and Kotlin while designing an Android project. The syntax of Java and Kotlin differs in many aspects but their compilation process is almost the same. Code of both the languages gets compiled into bytecode that is executable on Java Virtual Machine(JVM). Thus if one can derive the bytecode of compiled Kotlin file, it can be decompiled in order to produce the equivalent Java code. Android Studio does exactly the same to carry out the code conversion from Kotlin to Java. Developers may have many reasons to convert the Kotlin code into Java such as:

• To integrate features that are easy to implement in Java language.
• To resolve some performance issue that is difficult to locate in Kotlin.
• To remove the Kotlin code from the project files.

Code Conversion

Step 1: Open Kotlin Class/File

Open the Kotlin Class/File which is to be converted into Java. Consider the code of the MainActivity file mentioned below for the conversion.

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How to Convert Java Code to Kotlin Code in Android Studio?

In Google I/O 2017, Kotlin has been declared as an official language for Android app development. This language gains popularity among developers very quickly because of its similarities as well as interoperable with Javalanguage. One can mix code of Java and Kotlin while designing an Android project. Some of the major challenges faced by developers like avoiding null pointer exceptions are easily handled by Kotlin. Because of all these reasons, it became essential to learn Kotlin. However, Android Studio takes care of this need. Developers can easily convert their Java code into Kotlin in Android Studio. There can be 2 scenarios in front of developers:

• Converting a complete Java File/Class into Kotlin File/Class
• Add a new Kotlin file/class in the project and convert a piece of Java code.

This article broadly describes the steps involved in performing code conversion in both cases.

Code Conversion

Method 1: Converting a Complete Class/File into Kotlin

Step 1: Open source code file

Open the java source code file that is to be converted. Consider the given code of the MainActivity file that is to be converted into Kotlin.

Step 2: Select the option

From the left-hand side Option menu, select Android Project and right-click on the source code file. Select the option “Convert Java File to Kotlin File”. One can also use the shortcut command “Ctrl+Alt+Shift+K” while the file is opened in Android Studio.

A dialog box will appear that asks permission to configure Kotlin in Project. To carry out the code conversion it is necessary to grant this permission. Further, select the “All modules” option and choose the latest Kotlin compiler installed on the computer. After clicking “OK”, Android Studio will make some changes in the app module build.gradle file to perform code conversion successfully.

Step 3: Produce Kotlin file

Again select the “Convert Java File to Kotlin File” option by right click on the java class/file. This time the required conversion will happen and the file extension will get changed from .java to .kt. Below is the equivalent Kotlin code produced on converting the above mentioned MainActivity.java file.

Kotlin

Method 2: Adding a Separate Kotlin File into the Project

Android Studio allows the mixing of Java and Kotlin code in a project. If there is a requirement to reuse a piece of Java code by writing it in Kotlin, one can follow the below-mentioned steps.

Step 1: Create a Kotlin Class/File

Create a new Class/File of Kotlin extension inside the java folder of the application’s project file. Give it a desired name. Once the file is created, Android Studio will show an alert message that “Kotlin is not configured”.

Step 2: Configure Kotlin into the Project

Click on the “configure” option present on the alert message. A dialog box will appear, select “All modules” and choose the latest Kotlin compiler installed on the computer. Click “OK” and let the changes take place in build.gradle files.

Step 3: Copy and Paste

Once Android Studio finished the build of project files, open the created Kotlin Class/File. Copy the Java code which is to be converted. Paste that code in the created file/class having Kotlin extension. That Java code will get converted automatically into Kotlin by the Android Studio.

Advantages of Kotlin Over Java

1. Kotlin codes are more concise than Java.
2. It is interoperable(compatible) with Java.
3. Kotlin resolves nullability issues by placing “Null” in its type system.
4. Cleaner and safer code.

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Java Program to Convert English Text to Morse Code and Vice-Versa

Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called dots and dashes. Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: “a” maps to “.-“, “b” maps to “-…”, “c” maps to “-.-.”, and so on.

For convenience, the full table for the 26 letters of the English alphabet is given below:

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Table:

1. To convert the given English letter to Morse Code and vice versa using iteration

Example:

Approach:

1. Store all the alphabet in an array named in this code is letter[] same here store all the alphabet in another array named code[].
2. Convert the input string to char array str[].
3. Iteratively match the character position with a letter in the letter array.
4. Find its character position in that letter[] array and using that position returns the character present at that position from the code[] array.
5. Iteratively find all Morse Code for all character in an input string and vice versa.

Below is the implementation of the above approach.

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