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Jarno Walgemoed jwalgemoed

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View examplekotlin.kt
class SomeClass {
// Kotlin allows this, as you can specify the intended type here
var property: String
}
View example-collection.java
// Classic declaration
ArrayList<Integer> list = new ArrayList<Integer>();
// But honestly, since Java 7 Java we can use the diamond operator <> (or omit it entirely)
ArrayList<Integer> list = new ArrayList();
// Var declaration
var list = new ArrayList<Integer>();
View basic.java
// Classic declaration, we are repeating ourselves
Integer ten = new Integer(10);
// New declaration, using 'var'
var ten = new Integer(10);
View interface.java
// We can explicitly work against interfaces
List<String> list = new ArrayList(); // type: List<String>
// Using var, we can't do this without casting
var list = new ArrayList<String>(); // Inferred type ArrayList<String>
var list = (List)new ArrayList<String>(); // Inferred type List<String>
View example2.java
// Can't use the local variable type inference with fields
public class SomeClass {
// Not allowed, var is only available for local variables
var property = "";
}
// Can't leave values unitialzed
var uninitialized; // No way to infer the type
// Can't just assign null to var to reassign later (but workaround available)
View method.java
var variable = returnValue(); // Type is inferred from the return type of the method
// Method declaration
public String returnValue() {
return "w00p";
}
View example3.java
var strings = Arrays.asList("a", "b", "c");
for(var str: strings) {
System.out.println(str);
}
View userclass.kt
data class User(val name: String?, val email: String?) {
fun isValid() = !name.isNullOrBlank() && name.length > 3
&& !email.isNullOrBlank() && email.length > 3
}
View withcontract.kt
@ExperimentalContracts
fun User?.isComplete(): Boolean {
contract { returns(true) implies (this@isComplete != null) }
return this != null && this.isValid()
}
View contract.kt
contract {
returns(true) implies (this@isComplete != null)
}