#멋쟁이사자처럼 #부트캠프 #백엔드 #JAVA

실습 문제

Primitive Type VS Reference Type

public class Main {
    public static void main(String[] args) {
        int i = 10;
        int j = i;

        i += 10;
        System.out.println("i: " + i); // 20
        System.out.println("j: " + j); // 10

        int[] iArr1 = {10};
        int[] iArr2 = iArr1;

        iArr1[0] += 10;

        System.out.println("iArr1[0]: " + iArr1[0]); // 20
        System.out.println("iArr2[0]: " + iArr2[0]); // 20
    }
}

System.exit()

public class Main {
    public static void main(String[] args) {
        System.out.println(args.length);

        if (args.length == 0) {
            System.out.println("You need at least one program argument.");
            System.exit(0);
        }

        for (String str : args) {
            System.out.println(str);
        }
    }
}

Variable Arguments (Varargs)

Variable Arguments (Varargs) in Java is a method that takes a variable number of arguments. Variable Arguments in Java simplifies the creation of methods that need to take a variable number of arguments.

public class Main {
    public static int sum(int... args) {
        System.out.println("print1 method - length of args: " + args.length);
        int sum = 0;
        for (int i = 0; i < args.length; i++) {
            sum += args[i];
        }
        return sum;
    }

    public static void main(String[] args) {
        System.out.println(sum(5, 10));
        System.out.println(sum(1, 2, 4, 2));
        System.out.println(sum(3, 1, 2, 3, 4, 1));
    }
}

Practice: Calculator

public class Calculator {
    private String modelNumber;

    public String getSystemInfo() {
        return modelNumber;
    }

    public double add(double a, double b) {
        return a + b;
    }

    public double subtract(double a, double b) {
        return a - b;
    }

    public double divide(double a, double b) {
        return a / b;
    }

    public double multiply(double a, double b) {
        return a * b;
    }
}

Practice: Math.random()

public class Main {
    public static void main(String[] args) {
        // 0 <= a< 1
        double a = Math.random();
        System.out.println(a);

        // 0 <= b <= 45
        int b = (int) (Math.random() * 45) + 1;
        System.out.println(b);
    }
}