Understand the power of Java functions

Java functions are code reuse tools that can be used to define repeatable tasks, including: Defining functions: using the public return type function name (parameter) form. Calling a function: Use the instance name.function name (actual parameters) format.

Understand the advantages of Java functions

Java functions are powerful code reuse tools that help developers define Repeatable tasks. Here's how to define and use Java functions:

Define Java functions

public class FunctionDemo {

    // 定义一个名称为 sum 的函数，接收两个参数并返回它们的和
    public int sum(int num1, int num2) {
        return num1 + num2;
    }

    // 定义一个名称为 printMessage 的函数，接收一个参数并打印消息
    public void printMessage(String message) {
        System.out.println(message);
    }

    // 主函数
    public static void main(String[] args) {
        // 创建 FunctionDemo 类的实例
        FunctionDemo functionDemo = new FunctionDemo();

        // 调用 sum 函数并打印结果
        int result = functionDemo.sum(10, 20);
        System.out.println("Sum: " + result);

        // 调用 printMessage 函数并打印消息
        functionDemo.printMessage("你好，世界！");
    }
}

In this example:

• ##FunctionDemo Class contains defined functions.
• sum The function receives two integer parameters and returns their sum.
• printMessage The function receives a string parameter and prints the message.
• main The method is the entry point of the program and is used to call functions.

Practical case: Using Java functions to implement a simple calculator

Let us create a simple calculator class to demonstrate Java functions:

public class Calculator {

    // 定义加法函数
    public int add(int num1, int num2) {
        return num1 + num2;
    }

    // 定义减法函数
    public int subtract(int num1, int num2) {
        return num1 - num2;
    }

    // 定义乘法函数
    public int multiply(int num1, int num2) {
        return num1 * num2;
    }

    // 定义除法函数
    public double divide(int num1, int num2) {
        return (double) num1 / num2;
    }

    // 主函数
    public static void main(String[] args) {
        // 创建 Calculator 类的实例
        Calculator calculator = new Calculator();

        // 调用加法函数并打印结果
        int addResult = calculator.add(10, 20);
        System.out.println("Sum: " + addResult);

        // 调用减法函数并打印结果
        int subtractResult = calculator.subtract(20, 10);
        System.out.println("Difference: " + subtractResult);

        // 调用乘法函数并打印结果
        int multiplyResult = calculator.multiply(10, 20);
        System.out.println("Product: " + multiplyResult);

        // 调用除法函数并打印结果
        double divideResult = calculator.divide(20, 10);
        System.out.println("Quotient: " + divideResult);
    }
}

In this example:

• Calculator class contains functions for addition, subtraction, multiplication, and division.
• main method is used to call the function and print the result.

These examples show how Java functions can help you create reusable blocks of code and simplify your applications.

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