4.2.5 The boolean Type and boolean Values

The boolean type represents a logical quantity with two possible values, indicated by the literals true and false (§3.10.3). The boolean operators are:

• The relational operators == and != (§15.20.2)
• The logical-complement operator ! (§15.14.6)
• The logical operators &, ^, and | (§15.21.2)
• The conditional-and and conditional-or operators && (§15.22) and || (§15.23)
• The conditional operator ? : (§15.24)
• The string concatenation operator + (§15.17.1), which, when given a String operand and a boolean operand, will convert the boolean operand to a String (either "true" or "false"), and then produce a newly created String that is the concatenation of the two strings

Boolean expressions determine the control flow in several kinds of statements:

• The if statement (§14.8)
• The while statement (§14.10)
• The do statement (§14.11)
• The for statement (§14.12)

A boolean expression also determines which subexpression is evaluated in the conditional ? : operator (§15.24).

Only boolean expressions can be used in control flow statements and as the first operand of the conditional operator ? :. An integer x can be converted to a boolean, following the C language convention that any nonzero value is true, by the expression x!=0. An object reference obj can be converted to a boolean, following the C language convention that any reference other than null is true, by the expression obj!=null.

A cast of a boolean value to type boolean is allowed (§5.1.1); no other casts on type boolean are allowed. A boolean can be converted to a string by string conversion (§5.4).