Java 方法（方法的定义,可变参数,参数的传递问题,方法重载,方法签名)

public class MethodBody {

    // 1.代码块
    {
        System.out.println("【{}】是方法体");
    }

    // 2.静态代码块
    static {
        System.out.println("【static {}】是方法体");
    }

    // 3.方法
    public void run(int age) {
        System.out.println("方法的花括号中是方法体");

        // 4.if
        if (age == 18) {
            System.out.println("if 语句的花括号中是方法体");
        }

        // 5.for
        for (int i = 0; i < age; i++) {
            System.out.println("for 循环的花括号中是方法体");
        }

        // 6.while
        while (age > 50) {
            System.out.println("while 循环的花括号中是方法体");
        }

        // 7.switch-case
        switch (age) {
            // 错误：在该区域写代码是错误的（该区域不是方法体）
            // System.out.println(age); // ERROR
            case 1: {
                System.out.println("switch 语句的 case 语句块是方法体");
            }
        }

        // 8.do-while
        do {
            System.out.println("do-while 循环的花括号中是方法体");
        } while (age < 5);
    }

}

public class CreateMethodDemo {
    public static void main(String[] args) {
        int sum1 = CreateMethodDemo.sumOne2Hundred(1, 100);
        // sum1 = 5050
        System.out.println("sum1 = " + sum1);

        int sum2 = CreateMethodDemo.sumOne2Hundred(1, 1000);
        // sum2 = 500500
        System.out.println("sum2 = " + sum2);

        int sum3 = CreateMethodDemo.sumOne2Hundred(1, 10000);
        // sum3 = 50005000
        System.out.println("sum3 = " + sum3);
    }
    
    private static int sumOne2Hundred(int start, int end) {
        int sum = 0;

        for (int i = start; i <= end; i++) {
            sum += i;
        }
        return sum;
    }
}

public class VariableParameter {
    public static void main(String[] args) {
        int[] arr = {2, 5, 6, 7, 66, 53};
        VariableParameter vp = new VariableParameter();
        // sumByArr = 139
        System.out.println(vp.sumByArr(arr));
    }

    
    private String sumByArr(int[] arr) {
        if (arr == null || arr.length < 1) return "arr 数组为 null, 为数组元素为 0";

        int sum = 0;
        for (int i = 0; i < arr.length; i++) {
            sum += arr[i];
        }
        return "sumByArr = " + sum; 
    }
}

public class VariableParameter {

    public static void main(String[] args) {
        VariableParameter vp = new VariableParameter();
        // 当 sumByVariable1Parameter 的参数列表中一个【值】都没有
        // 的时候, 返回值是可变参数类型的默认值
        int sum = vp.sumByVariable1Parameter(2, 5, 6, 7, 66, 53);
        // sumByVariable1Parameter = 139
        System.out.println("sumByVariable1Parameter = " + sum);
    }

    
    private int sumByVariable1Parameter(int... nums) {
        int sum = 0;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
        }
        return sum;
    }
}

public class VariableParameter {

    public static void main(String[] args) {
        String info = String.fORMat("name: %s; age: %d; money: %f", 
    							"庆医", 10, 895863.99);
        // info = name: 庆医; age: 10; money: 895863.990000
        System.out.println("info = " + info);
    }
}

public class ArgumentsPassingTest {

    public static void main(String[] args) {
        int n = 10;
        test(n); // 值传递（v 和 n 没有关系）
        // n = 10
        System.out.println("n = " + n);
    }
    private static void test(int v) { // v = 10
        v = 20;
    }
}

public class ArgumentsPassingTest {

    public static void main(String[] args) {
        int test = test(66);
        // test = 88
        System.out.println("test = " + test);
    }

    private static int test(int param) {
        param = 88;
        return param;
    }
}

public class ArgumentsPassingTest {

    public static void main(String[] args) {
        int[] nums = {1, 2, 3};
        test(nums);
        // nums = [1, 66, 3]
        System.out.println("nums = " + Arrays.toString(nums));
    }
    private static void test(int[] param) {
        param[1] = 66;
    }
}

public class ArgumentsPassingTest {

    public static void main(String[] args) {
        int[] test = test();

        // test = [1314, 520, 666]
        System.out.println("test = " + Arrays.toString(test));
    }
    private static int[] test() {
        int[] ints = {1314, 520, 666};
        return ints;
    }
}

private static void test(double pai, String name, int age) {
    return null;
}

private static int[] test(double weight, String name, int age) {
    return null;
}
private static int[] test(int age, double weight, String name) {
    return null;
}