[英]Why does java.util.concurrent.TimeUnit.convert throw an AbstractMethodError instead of being abstract
java.util.concurrent.TimeUnit
有這個來源:
public long convert(long sourceDuration, TimeUnit sourceUnit) {
throw new AbstractMethodError();
}
為什么這不是一個abstract
方法
abstract int excessNanos(long d, long m);
方法聲明上方的單行注釋如下:
// To maintain full signature compatibility with 1.5, and to improve the
// clarity of the generated javadoc (see 6287639: Abstract methods in
// enum classes should not be listed as abstract), method convert
// etc. are not declared abstract but otherwise act as abstract methods.
在這里, 6287639
是bug id,它說,
JDK-6287639:枚舉類中的抽象方法不應列為抽象方法
現在考慮以下enum
將其視為類和每個枚舉常量作為Object
,很明顯,如果我們創建一些抽象的Object
,我們必須提供實現並避免這種convert
不是abstract
,
enum Blocks {
A1, B1, C1;
// It will say enum constant must implement
// the abstract method test
abstract int test();
}
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