Java | Фишки и трюки

class Test {
   int a = 0b1101010110;
   public static void main(String[] args) {
       System.out.println("Hello world!");       
   }
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

management.endpoints.web.exposure.include=health,info,metrics
management.endpoint.health.show-details=always

public class Quest {
    public static void main(String[] args) {
        System.out.println(calc(10, 5));
    }

    private static int calc(int i, int j) {
        int result = i + j;
        return result;

        result = i - j;
        return result;
    }
}

public class Quest {
    public static void main(String[] args) {
        System.out.println(concat1() < concat2());
    }
    private static long concat1() {
        long start = System.nanoTime();
        String s = "";
        for (int i = 0; i < 1000; i++) {
            s += "-" + i;
        }
        return System.nanoTime() - start;
    }

    private static long concat2() {
        long start = System.nanoTime();
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < 1000; i++) {
            s.append("-" + i);
        }
        return System.nanoTime() - start;
    }
}

Parent parent = new Child();
if (parent instanceof Child) {
    Child child = (Child) parent;
}

public final class Objects {
    private Objects() {
        throw new AssertionError("No java.util.Objects instances for you!");
    }
    ...
}

public static boolean equals(Object a, Object b) {
    return (a == b) || (a != null && a.equals(b));
}

public static String toString(Object o) {
    return String.valueOf(o);
}

public static String toString(Object o, String nullDefault) {
    return (o != null) ? o.toString() : nullDefault;
}

public static <T> T requireNonNull(T obj) {
    if (obj == null)
        throw new NullPointerException();
    return obj;
}

public static boolean isNull(Object obj) {
    return obj == null;
}

public static boolean nonNull(Object obj) {
    return obj != null;
}

public class Quest {
    public static void main(String[] args) {
        Short b = 50;
        inc(b);
        System.out.println(b);
    }
    private static void inc(Short num) {
        num++;
    }
}

INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...)
ON CONFLICT (conflict_target) 
DO UPDATE SET column1 = value1, column2 = value2, ...;

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    username TEXT UNIQUE,
    email TEXT
);

INSERT INTO users (id, username, email)
VALUES (1, 'user1', 'user1@example.com')
ON CONFLICT
DO NOTHING;

INSERT INTO users (id, username, email)
VALUES (1, 'user1', 'user1@example.com')
ON CONFLICT
DO NOTHING;