What is the difference between Java functions and Kotlin language functions?
Apr 24, 2024 am 08:24 AMThe difference between Java and Kotlin functions: Syntax: Java functions need to specify parameter types and names, while Kotlin can omit the type and use lambda expressions; Parameters: Kotlin can omit parameter types using a more concise syntax; Return value: Kotlin can Omit the return value type, which defaults to Unit; extension function: Kotlin can add new functions to existing classes, while Java needs to implement similar functions through inheritance; instance method call: Kotlin can omit the object name and use a more concise syntax.
The difference between Java functions and Kotlin language functions
Syntax:
- Java function:
public static void main(String[] args)
- Kotlin function:
fun main(args: Array<string>)</string>
Parameters:
- Java function: parameter type and name need to be specified explicitly
- Kotlin function: parameter type can be omitted, parameter name is optional
Return value:
- Java function: the return value type must be specified
- Kotlin function: the return value type can be omitted ( Default is
Unit
)
Lambda expression:
- Java: Need to implement the interface and override the method
- Kotlin: Use
{}
directly to define lambda expressions
Example:
// Java 函數(shù) public static void main(String[] args) { System.out.println("Hello Java!"); }
// Kotlin 函數(shù) fun main(args: Array<String>) { println("Hello Kotlin!") }
Extension function:
- Kotlin’s unique feature, you can add new functions to existing classes
- Java needs to inherit or use proxy classes to achieve similar functions
Instance method call:
- Java: via object name
.
Method name - Kotlin: via object
.
Method name (optional)
Practical case:
Consider a function that calculates the sum of two numbers:
// Java 函數(shù) public static int add(int a, int b) { return a + b; }
// Kotlin 函數(shù) fun add(a: Int, b: Int) = a + b
In Java, you need to specify parameter types and names explicitly. But in Kotlin, you can omit parameter types and use a cleaner syntax. In addition, in Kotlin, you can add a plus
function to the Int
class through an extension function to make the code more readable:
fun Int.plus(other: Int) = this + other
In this way, you The sum of numbers can be calculated like this:
val sum = 10.plus(20)
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