[Kotlin] Android Java 와 Kotlin 몇가지 문법 비교

Java

Integer.parseInt(someValue)

 

Kotlin

someValue.toInt()

 

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Java

if ( "100".equals(someValue) ) {  }

Kotlin

if( someValue == "100" ) { }

 

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Java

Object someValue = new String("hello");
if ( someValue instanceof String ) {
    // OK
}

Kotlin

var someValue: Any = "hello"
if ( someValue is String ){
    // OK
}

 

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Java

class MainActivity : AppCompatActivity() {

Kotlin

class MainActivity : AppCompatActivity() {

 

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Java

Button button = findViewById(R.id.button);
button.setOnClickListener(new View.onClickListener(){
    @override
    public void onClick(View view){
        Toast.makeText(getApplicationContext(), "Hello~ Bryan~!", Toast.LENGTH_LONG).show();
    }
});

Kotlin

binding.button.setOnClickListener {
    Toast.makeText(applicationContext, "Hello~ Bryan~!", Toast.LENGTH_LONG).show()
}

 

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Java

public void show(String message) { ... }

Kotlin

fun show(message: String) { ... }

 

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Java

public int add(int a, int b) {
    return a + b;
}

Kotlin

fun add(a:Int, b:Int):Int {
    return a + b
}

fun add(a:Int, b:Int):Int = a + b

fun add(a:Int, b:Int) = a + b

val add = { a:Int, b:Int -> a + b }