연산자

문자열 비교 시: .equals()

and : &&

or : ||

Operator1

package operator;

public class Operator1 {
    public static void main(String[] args) {
        //변수 초기화
        int a = 5;
        int b = 2;

        // 덧셈
        int sum = a+b;
        System.out.println("a + b = " + sum);

        //뺄셈
        int diff = a-b;
        System.out.println("a - b = " + diff);

        //곱셈
        int multi = a*b;
        System.out.println("a * b = " + multi);

        //나눗셈
        int div = a/b;  // 정수형이므로 2.5가 아닌 2로 나옴
        System.out.println("a / b = " + div);

        //나머지
        int mod = a%b;
        System.out.println("a % b = " + mod);
        
        // 10/0 >> 0으로 나누면 오류 발생
    }
}

Operator2

package operator;

import java.sql.Struct;

public class Operator2 {
    public static void main(String[] args) {

        //문자열과 문자열 더하기1
        String result1 = "hello " + "world";
        System.out.println(result1);

        //문자열과 문자열 더하기2
        String s1 = "string1";
        String s2 = "string2";
        String result2 = s1 + s2;
        System.out.println(result2);

        //문자열과 숫자 더하기1
        String result3 = "a + b = " + 10;
        System.out.println(result3);

        //문자열과 숫자 더하기2
        int num = 20;
        String str = "a + b = ";
        String result4 = str + num;
        System.out.println(result4);

    }
}

Operator3

package operator;

public class Operator3 {
    public static void main(String[] args) {

        int sum1 = 1 + 2 * 3;   //1 + (2 * 3)
        int sum2 = (1 + 2) * 3;
        System.out.println("sum1 = " + sum1);
        System.out.println("sum2 = " + sum2);
    }
}

Operator4

package operator;

public class Operator4 {
    public static void main(String[] args) {
        int sum3 = 2 * 2 + 3 * 3;
        int sum4 = (2 * 2) + (3 * 3);

        System.out.println("sum3 = " + sum3);
        System.out.println("sum4 = " + sum4);
    }
}

OperatorAdd1

package operator;

public class OperatorAdd1 {
    public static void main(String[] args) {
        int a = 0;

        a = a+1;
        System.out.println("a = "  + a);

        a = a+1;
        System.out.println("a = "  + a);

        //증감 연산자
        ++a;    // a = a + 1
        System.out.println("a = "  + a);

        ++a;    // a = a + 1
        System.out.println("a = "  + a);
    }
}

OperatorAdd2

package operator;

public class OperatorAdd2 {
    public static void main(String[] args) {
        //전위 증감 연산자
        // a의 값을 먼저 증가시키고, 그 결과를 b에 대입
        int a = 1;
        int b = 0;
        b = ++a;
        System.out.println("a = "+ a + ", b = " + b);

        //후위 증감 연산자
        // b에 결과를 먼저 대입하고 a값을 증가
        a = 1;
        b = 0;
        b = a++;
        System.out.println("a = "+ a + ", b = " + b);
    }
}

Comp1

package operator;

public class Comp1 {
    public static void main(String[] args) {
        int a = 2;
        int b = 3;

        System.out.println(a == b);
        System.out.println(a != b);
        System.out.println(a > b);
        System.out.println(a < b);
        System.out.println(a >= b);
        System.out.println(a <= b);

        boolean result = a == b;    //false
        System.out.println(result);
    }
}

Comp2

package operator;

public class Comp2 {
    public static void main(String[] args) {
        String str1 = "문자열1";
        String str2 = "문자열2";

        boolean result1 = "hello".equals("hello");
        boolean result2 = str1.equals("문자열1");
        boolean result3 = str1.equals(str2);

        System.out.println("result1 = " + result1);
        System.out.println("result2 = " + result2);
        System.out.println("result3 = " + result3);

    }
}

Logical1

package operator;

public class Logical1 {
    public static void main(String[] args) {
        System.out.println("&&: AND 연산");
        System.out.println(true && true); // true
        System.out.println(true && false); // false
        System.out.println(false && false); // false

        System.out.println("||: OR 연산");
        System.out.println(true || true); // true
        System.out.println(true || false); // true
        System.out.println(false || false); // false

        System.out.println("! 연산");
        System.out.println(!true); // false
        System.out.println(!false); // true

        System.out.println("변수 활용");
        boolean a = true;
        boolean b = false;

        System.out.println(a && b); // false
        System.out.println(a || b); // true
        System.out.println(!a); // false
        System.out.println(!b); // true
    }
}

Logical2

package operator;

public class Logical2 {
    public static void main(String[] args) {
        int a = 15;
        // a는 10보다 크고 20보다 작다
        boolean result = a > 10 && a < 20; // (a > 10) && (a < 20)
        System.out.println("result = " + result);
    }
}

Assign1

package operator;

public class Assign1 {
    public static void main(String[] args) {
        int a = 5;
        a += 3;
        a -= 2;
        a *= 4;
        a /= 3;
        a %= 5;
        System.out.println(a);

    }
}

OperationEx1

package operator;

public class OperationEx1 {
    public static void main(String[] args) {
        int num1 = 10, num2 = 20, num3 = 30;
        int sum = num1 + num2 + num3;
        int average = sum / 3;

        System.out.println(sum);
        System.out.println(average);
    }
}

OperationEx2

package operator;

public class OperationEx2 {
    public static void main(String[] args) {
        double val1 = 1.5;
        double val2 = 2.5;
        double val3 = 3.5;

        double sum = val1 + val2 + val3;
        double average = sum / 3;

        System.out.println(sum);
        System.out.println(average);
    }
}

OperationEx3

package operator;

public class OperationEx3 {
    public static void main(String[] args) {
        int score = 50;
        boolean result = 80 <=score && score <= 100;
        System.out.println(result);
    }
}