// 方法定義
    public static 方法返回值 方法名稱（參數(shù)類型 形參){
        方法體代碼;
        return 返回值;
    }
 
    public static void main(String[] args) {
        // 方法調(diào)用
        返回值變量 = 方法名稱 (實(shí)參);
    }

public class TestDemo {
    // 方法定義
    public static int Add(int x,int y){
        int sum = x+ y;
        return sum;
    }
 
    public static void main(String[] args) {
        //方法的調(diào)用
        Add(10,20);
        System.out.println(Add(10,20));
    }
}

public class Test1 {
    public static void swap(int a,int b){
        int temp = a;
        a = b;
        b = temp;
    }
 
    public static void main(String[] args) {
        int a = 10;
        int b = 20;
        System.out.println("交換實(shí)參前："+a+" "+b);
        swap(a,b);
        System.out.println("交換實(shí)參后："+a+" "+b);
    }
}

public class Test2 {
    public static int addInt(int a, int b){
        int sum = a+b;
        return sum;
    }
 
    public static double addDouble(double a,double b){
        double sum = a+b;
        return sum;
    }
 
    public static void main(String[] args) {
        double a = 10.5;
        double b = 20.5;
        addDouble(a,b);
        System.out.println(addDouble(a,b));
    }
}

public class Test2 {
    public static int add(int a, int b){
        int sum = a+b;
        return sum;
    }
 
    public static double add(double a,double b){
        double sum = a+b;
        return sum;
    }
 
    public static void main(String[] args) {
        double a = 10.5;
        double b = 20.5;
        add(a,b);
        System.out.println(add(a,b));
    }
}

public class Test3 {
    public static int fac(int n){
        if(n==1){
            return 1;
        }
        int temp = n*fac(n-1);
        return temp;
    }
 
    public static void main(String[] args) {
        System.out.println(fac(3));
    }
}

public class Demo1 {
    public static void print(int n){
        if(n>9){
            print(n/10);
        }
       System.out.print(n%10+" ");;
    }
 
    public static void main(String[] args) {
        int n = 1234;
        print(n);
    }
}

public class Demo2 {
    public static int func(int n){
        if(n!=0){
            n += func(n-1);
        }
        return n;
    }
    public static void main(String[] args) {
        System.out.println(func(10));
    }
}

public class Demo3 {
    public static int func(int n){
        if(n<10){
            return n;
        }
        return n%10+func(n/10);
    }
 
    public static void main(String[] args) {
        System.out.println(func(1792));
    }
}

public class Demo4 {
    public static int fib(int n){
        if(n==1 || n == 2){
            return 1;
        }else{
            return fib(n-1)+fib(n-2);
        }
    }
 
    public static void main(String[] args) {
        System.out.println(fib(1));
        System.out.println(fib(2));
        System.out.println(fib(3));
        System.out.println(fib(4));
        System.out.println(fib(123456));
    }
}

public class Demo4 {
    
    public static int fib2(int n){
        if(n==1 || n==2){
            return 1;
        }
        int f1 = 1;
        int f2 = 1;
        int f3 = 0;
        for (int i = 3; i <= n; i++) {
            f3 = f1 + f2;
            f1 = f2;
            f2 = f3;
        }
        return f3;
    }
 
    public static void main(String[] args) {
        System.out.println(fib2(1));
        System.out.println(fib2(2));
        System.out.println(fib2(3));
        System.out.println(fib2(4));
        System.out.println(fib2(40));
    }
}