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8 - White Space

8.1 Blank Lines

Blank lines improve readability by setting off sections of code that are logically related.

Two blank lines should always be used in the following circumstances:

  • Between sections of a source file
  • Between class and interface definitions

One blank line should always be used in the following circumstances:

  • Between methods
  • Between the local variables in a method and its first statement
  • Before a block (see section 5.1.1) or single-line (see section 5.1.2) comment
  • Between logical sections inside a method to improve readability

8.2 Blank Spaces

Blank spaces should be used in the following circumstances:

  • A keyword followed by a parenthesis should be separated by a space. Example:

        while (true) {

Note that a blank space should not be used between a method name and its opening parenthesis. This helps to distinguish keywords from method calls.

  • A blank space should appear after commas in argument lists.
  • All binary operators except . should be separated from their operands by spaces. Blank spaces should never separate unary operators such as unary minus, increment ("++"), and decrement ("--") from their operands. Example:

    a += c + d;
    a = (a + b) / (c * d);
    while (d++ = s++) {
    printSize("size is " + foo + "\n");

  • The expressions in a for statement should be separated by blank spaces. Example:

for (expr1; expr2; expr3)

  • Casts should be followed by a blank space. Examples:

myMethod((byte) aNum, (Object) x);
myMethod((int) (cp + 5), ((int) (i + 3)) 
                                  + 1);