Странная джава

является точкой зрения автора и не является официальной позицией той

или иной компании. Все возможные совпадения случайны.
Пожалуйста, не принимайте решений на основе этого доклада. В противном случае воспользуйтесь услугами профессионалов.

{ Integer a = 12;

Integer b = 12; if (a == b) System.out.println("bingo!"); } }

Вывод:

bingo!

in the range -128 to 127, * inclusive, and may

cache other values outside of this range. *… * @since 1.5 */ public static Integer valueOf(int i) { if (i >= IntegerCache.low && i <= IntegerCache.high) return IntegerCache.cache[i + (-IntegerCache.low)]; return new Integer(i); }

{ String s = null;

s += 10; System.out.println(s); } }

Вывод:

null10

the reference is null, it is converted to the string

"null" (four ASCII characters n, u, l, l). Otherwise, the conversion is performed as if by an invocation of the toString method of the referenced object with no arguments; but if the result of invoking the toString method is null, then the string "null" is used instead.

JLS, 15.18.1. String Concatenation Operator +
s = new StringBuilder(String.valueOf(s))
.append(String.valueOf(10)).toString();

{ "Hello world!".chars().forEach(System.out::print); } }
Вывод:
721011081081113211911111410810033

{@code char} values * from this sequence. Any char which

maps to a surrogate code * point is passed through uninterpreted. * *

If the sequence is mutated while the stream is being read, the * result is undefined. * * @return an IntStream of char values from this sequence * @since 1.8 */ public default IntStream chars() {

{
int j = 0;

for (int i = 0; i < 100; i++)
j = j++;
System.out.println(j);
}}

Вывод:

0

the operand expression completes abruptly, then the postfix increment expression

completes abruptly for the same reason and no incrementation occurs. Otherwise, the value 1 is added to the value of the variable and the sum is stored back into the variable. 

int tmp = j;
j = j + 1;
j = tmp;

… и никакой магии!

кувшинки на кувшинку

{ System.out.println(decision()); } static boolean

decision() { try { return true; } finally { return false; } }}

Вывод:

false

the finally block is executed, and then there is a choice:
If the finally block

completes normally, then the try statement completes normally
 If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S.

и кладем туда жирафа

{ try {

throw new NullPointerException("NullPointerException 1"); } catch (NullPointerException e) { throw new NullPointerException("NullPointerException 2"); } finally { return; } } }

Вывод:

the finally block is executed. Then there is a choice:
If the finally block completes

normally, then the try statement completes abruptly for reason R.
If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S (and reason R is discarded).

это не значит,
что так оно и есть. Возможно, вы чего-то

не знаете

BigInteger firstParam = new BigInteger("2");

BigInteger secondParam = new BigInteger(”2");

BigInteger total = BigInteger.ZERO;
total.add(firstParam);
total.add(secondParam);
System.out.println(total);
}}

Вывод:

0

Character, Boolean, Float, и Double – это immutable типы!

Neal Gafter. Java Puzzlers. Traps, Pitfalls, and Corner Cases
Joshua Bloch.

Effective Java: Second Edition
 Gayle Laakmann McDowell. Cracking the Coding Interview: 189 Programming Questions and Solutions