Difference between Java and Kotlin in Android with Examples

Kotlin was introduced for Android development as a modern alternative to Java, offering concise syntax, null safety, and many language-level improvements. Google announced Kotlin as the preferred language for Android development in 2019.

Code Comparison Examples

Kotlin reduces boilerplate code significantly compared to Java −

Setting Text on a View

// Java: requires casting and explicit reference
TextView displayText = (TextView) findViewById(R.id.textView);
displayText.setText("Hello World");

// Kotlin: concise with synthetic view binding
textView.setText("Hello World")

Null Safety

// Kotlin enforces null check at compile time
var value: String = "abc"
value = null   // Compilation error!

// To allow null, use nullable type
var nullable: String? = "abc"
nullable = null   // OK

Data Classes

// Java POJO: requires getters, setters, equals, hashCode, toString
public class User {
    private String name;
    private int age;
    public User(String name, int age) { this.name = name; this.age = age; }
    public String getName() { return name; }
    public int getAge() { return age; }
    // + setters, equals, hashCode, toString...
}

// Kotlin: one line generates everything
data class User(val name: String, val age: Int)

Key Differences

Conclusion

Kotlin offers more concise syntax, built-in null safety, data classes, and coroutines compared to Java, making Android development faster and less error-prone. Java remains fully supported and has a larger legacy codebase, but Kotlin is now the preferred language for new Android projects.