6.4.3 The Members of an Interface Type

The members of an interface type (§9.2) are fields and methods. The members of an interface are all of the following:

• Members inherited from any direct superinterfaces (§9.1.3)
• Members declared in the body of the interface (§9.1.4)

An interface may have two or more fields with the same simple name if they are declared in different interfaces and inherited. An attempt to refer to any such field by its simple name results in a compile-time error (§6.5.5.1, §9.2).

In the example:

interface Colors {
	int WHITE = 0, BLACK = 1;
}

interface Separates {
	int CYAN = 0, MAGENTA = 1, YELLOW = 2, BLACK = 3;
}
interface ColorsAndSeparates extends Colors, Separates {

	int DEFAULT = BLACK;								 	// compile-time error: ambiguous

}

the members of the interface ColorsAndSeparates include those members inherited from Colors and those inherited from Separates, namely WHITE, BLACK (first of two), CYAN, MAGENTA, YELLOW, and BLACK (second of two). The member name BLACK is ambiguous in the interface ColorsAndSeparates.