Question

Java的内置库（JDK）中是否有一个包含常量字段的接口示例？

从documentation开始，可以在界面中定义常量声明，但我不记得看到这样的声明。

public interface OperateCar {

   // constant declarations, if any
   ...
}

Answer 1

例如

package java.text;

public interface CharacterIterator extends Cloneable
{
    /**
     * Constant that is returned when the iterator has reached either the end
     * or the beginning of the text. The value is '\\uFFFF', the "not a
     * character" value which should not occur in any valid Unicode string.
     */
    public static final char DONE = '\uFFFF';

但通常，在JDK接口中很难找到常量，因为它不符合语言约定。

Answer 2

interface的每个字段都隐含public static final，从而使其成为常量。

所以：

public interface MyInterface {
    String FOO = "foo";
}

...与：

相同

public interface MyInterface {
    public static final String FOO = "foo";
}

Java SDK中的接口常量声明示例

2 个答案: