Java | Фишки и трюки
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Java: примеры кода, интересные фишки и полезные трюки

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public class Quest {
public static void main(String[] args) {
int j = 0;
for (int i = 0; i < 10; i++) {
j = j++;
}
System.out.println(j);
}
}

#java #quest
❤‍🔥4
public class Quest {
public static void main(String[] args) {
List<Integer> ints = List.of(1, 2, 3, 4, 5, 6, 7, 8, 9);
ints.stream()
.filter(i -> i % 2 == 0)
.skip(1)
.limit(1)
.forEach(System.out::print);
}
}

#java #quest
2
public class Quest {
public static void main(String[] args) {
int i = Integer.MAX_VALUE;
i++;
if (i == 0) {
System.out.println("ZERO");
} else if (i == Integer.MIN_VALUE) {
System.out.println("MIN");
}
}
}

#java #quest
2
public class Quest {
public static final int END = Integer.MAX_VALUE;
public static final int START = END - 100;

public static void main(String[] args) {
int count = 0;
for (int i = START; i <= END; i++) count++;
System.out.println(count);
}
}

#java #quest
5
public class Quest {
public static void main(String[] args) {
int minutes = 0;
for (int ms = 0; ms < 60 * 60 * 1000; ms++) {
if (ms % 60 * 1000 == 0) {
minutes++;
}
}
System.out.println(minutes);
}
}

#java #quest
1💘1
public class Quest {
public static void main(String[] args) {
Integer a = 128;
Integer b = 128;
System.out.print(a == b);

System.out.print("-");

Integer x = 1;
Integer y = 1;
System.out.print(x == y);
}
}

#java #quest
👍21
public class Survive {
private Survive internalInstance = new Survive();

public Survive() throws Exception {
throw new Exception("I'm not coming out");
}

public static void main(String[] args) {
try {
Survive b = new Survive();
System.out.println("WIN!");
} catch (Exception ex) {
System.out.println("LOSE!");
}
}
}


#java #quest
public class Quest {
public static void main(String[] args) {
int[][] tests = {
{6, 5, 4, 3, 2, 1},
{1, 2},
{1, 2, 3},
{1, 2, 3, 4},
{1}
};
int n = 0;
try {
int i = 0;
while (true) {
if (thirdElementIsThree(tests[i++])) n++;
}
} catch (ArrayIndexOutOfBoundsException e) {
}
System.out.println(n);
}

private static boolean thirdElementIsThree(int[] a) {
return (a.length >= 3) & (a[2] == 3);
}
}


#java #quest
5
public class Quest {
public static void main(String[] args) {
int a = 5;
int b = 10;
int result = multiply(a, b);
System.out.println(result);
}

public static int multiply(int x, int y) {
if (y == 0) {
return 0;
} else {
return x + multiply(x, y - 1);
}
}
}

#java #quest
4
public class Test {

public static int VAL;

{
VAL = 5;
}

public Test() {
VAL = 10;
}

public static void print() {
System.out.println(VAL);
}

}

public class Quest {
public static void main(String[] args) {
Test.print();
}
}


#java #quest
5
public class Quest {
public static void main(String[] args) {
final String pig = "length: 10";
final String dog = "length: " + pig.length();

System.out.println("Animals are equal: " + pig == dog);
}
}

#java #quest
👍2
public class Quest {
public static void main(String[] args) {
System.out.println(isEqual(1, 1));
}

private static boolean isEqual(int i, int j) {
return (i == j) ? null : false;
}
}


#java #quest
4
public class Quest {
private final String name;

Quest(String name) {
this.name = name;
}

private String name() {
return name;
}

private void reproduce() {
new Quest("reproduce") {
void printName() {
System.out.println(name());
}
}.printName();
}

public static void main(String[] args) {
new Quest("main").reproduce();
}
}


#java #quest
3
public class Null {
public static void greet() {
System.out.println("HI!");
}

public static void main(String[] args) {
((Null) null).greet();
}
}


#java #quest
3
public class Quest {
static {
main(new String[] { "Hello" });
}

public static void main(String[] args) {
System.out.print("Hi");
}
}


#java #quest
4
public class Quest {
public static void main(String[] args) {
Boolean b;
System.out.println(Boolean.TRUE.equals(!b));
}
}


#java #quest
6👎1
enum Month {
JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER
}

public class Quest {
public static void main(String[] args) {
Month m = Month.JANUARY;
String season = switch (m) {
case DECEMBER, JANUARY, FEBRUARY -> "Winter";
case MARCH, APRIL, MAY -> "Spring";
case JUNE, JULY, AUGUST -> "Summer";
case SEPTEMBER, OCTOBER -> "Autumn";
};
System.out.println(season);
}
}


#java #quest
8👎1
public class Quest {
public static void main(String[] args) {
List<Integer> list = Arrays.asList(1,2,3);
List<Integer> subList = list.subList(1, 2);
subList.set(0, 5);
System.out.println(list.get(1));
}
}


#java #quest
2👎1
public class Quest {
public static void main(String[] args) {
int b = 500;
int c = inc(b);
System.out.println(b==c);
}
private static int inc(int num) {
return num++;
}
}


#java #quest
2👎2
public class Quest {
public static void main(String[] args) {
System.out.print(op1() + op2() * op3());
}

private static int op1() {
System.out.print(1);
return 1;
}
private static int op2() {
System.out.print(2);
return 2;
}
private static int op3() {
System.out.print(3);
return 3;
}
}


#java #quest
👍3👎21