What is the difference and what are operators & and && e | and || in Java for?

Question

I was analyzing some possibilities for the implementation of an algorithm and I went to look up this & and |, and I read some topics in English but it’s not 100% clear to me what it’s for and where I can use it. Then I would like an explanation, clearer and with practical examples of how to use it. (And in my native language, in case: Português).

Questions

• What is the difference between operators & and &&?
• What is the operator for &?
• An example of use for the operator &?
• What is the difference between operators | and ||?
• What is the operator for |?
• An example of use for the operator |?

Answer 1

& is a binary operation, see more on Wikipedia - Binary logic, Example:

int a = 60; // Em binário, 60 é 0011 1100
int b = 13; // Em binário, 13 é 0000 1101
int c = a & b; // Complicado, mas quando os dois dígitos forem 1, o resultado será 1, se não será 0. Ou seja, "c" dará 0000 1100, que é 12.

&& means "and", or "and", for example:

if (1 == 1 && 6 > 9) {
    // Se 1 for igual a 1 E 6 for maior que 9, isso vai acontecer, no caso não, pois 6 não é maior que 9.
}

| is another binary operation, where if any of the binary digits are 1, the result will be one, example:

int a = 60; // Em binário, 60 é 0011 1100
int b = 13; // Em binário, 13 é 0000 1101
int c = a | b; // Quando um dos dígitos forem 1, o resultado será 1 também. "c" dará 0011 1101, que é 61.

|| means "or", or "or", for example:

if (1 == 1 || 6 > 9) {
    // Se 1 for igual a 1 OU 6 for maior que 9, isso vai acontecer, no caso sim, pois 1 é igual a 1, e isso já basta para o |.
}

Answer 2

The difference between the logical operators that use a symbol and two symbols is that when you use two is what is known as logic short circuit operators.

The logic short-circuit operator performs as little code as possible in order to process the logical operation, i.e., if you are making a comparison of the type if(false && true) when processing this part and find that soon the first result is false he does not even analyze the second part of logic, so it does not matter if the second part is true or false, for false && qualquerCoisa always gives false.

In general, short-circuit logic comparators are always used, as they will never be slower than non-short-circuit logic operators. However it is necessary to be aware of exceptional situations where the execution or not of the rest of the operators can change the program flow and generate an unexpected result, such as:

int a = 5;
if(++a > 5 || ++a > 6) a++; 
System.out.println(a);       //a==7

Against:

int b = 5;
if(++b > 5 | ++b > 6) b++; 
System.out.println(b);       //b==8

Example in Ideone

In the first case, for being a short circuit he makes the first ++a, checks that it is greater than 5 and does not continue to execute the code after the ||, for true OU qualquerCoisa is true. How did you give if(true) he enters the if and makes a++, making it 7.

In the second case, by not using short circuit operators it processes everything that is within the if, soon he makes ++b twice, resulting in if(true|true) which is the same thing as if(true), it enters the code inside the if and does b++ making it 8.