It is permissible to remove braces in case they are superfluous. This not only applies to the control statements if, for, while and do-while, but also to every block in general (remember a block is just a sequence of statements, local class declarations and local variable declaration statements within braces). Inserting and removing braces is mutually exclusive.

Single if

When enabled, braces around the body of single if statements are removed when possible.

Since 1.9.1

if (true) {
    break;
}

if (true)
    break;

if..else

When enabled, braces around the body of if...else statements are removed when possible.

if (true) {
    break;
} else {
    return;
}

if (true)
    break;
else
    return;

for

When enabled, braces around the body of for statements are removed when possible.

for (int i = 0; i < count; i++) {
    System.out.println(i);
}

for (int i = 0; i < count; i++)
    System.out.println(i);

while

When enabled, braces around the body of while statements are removed when possible.

while (!isDone) {
    doSomething();
}

while (!isDone)
    doSomething();

do...while

When enabled, braces around the body of do...while statements are removed when possible.

do {
  something();
} while (condition);

do
  something();
while (condition);

switch

When enabled, braces are removed around the body of labeled statements inside switch blocks when possible.

Since 1.8

switch (c) {
    case 'a':
    case 'b': {
        System.out.println();
        break;
    }
}

switch (c) {
    case 'a':
    case 'b':
        System.out.println();
        break;
}

Blocks

When enabled, arbitrary block braces are removed when possible.

{
    System.out.println();
}

System.out.println();