The Java® Language Specification, Java SE 7 Edition, Fourth Edition

14.15. The break Statement

A break statement transfers control out of an enclosing statement.

BreakStatement:    break Identifier_opt ;

A break statement with no label attempts to transfer control to the innermost enclosing switch, while, do, or for statement of the immediately enclosing method or initializer; this statement, which is called the break target, then immediately completes normally.

To be precise, a break statement with no label always completes abruptly, the reason being a break with no label.

If no switch, while, do, or for statement in the immediately enclosing method, constructor, or initializer contains the break statement, a compile-time error occurs.

A break statement with label Identifier attempts to transfer control to the ...