問題描述

public abstract class Rhythm { /** * @return duration between {@linkplain Note} in milliseconds */ public abstract long getDuration(); public void perform() {long duration = getDuration();try { Thread.sleep(duration);} catch (InterruptedException ie) { Thread.currentThread().interrupt(); throw new RuntimeException(ie);} }}

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@Override public void play(Rhythm rhythm, Note note, NoteCallback noteCallback){ rhythm.getDuration();//想在這里重寫getDuration方法，如何做到？ rhythm.perform(); note.getNoteValue(); noteCallback.notePlayed(note);}

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//重寫成如下形式 @Override public long getDuration(){ return (expectedMs); }

代碼附上。在play() 方法中如何直接重寫Rhythm類中的抽象方法getDuration()呢？ 創建rhythm對象是可以用匿名類的方法實例化的，那是實例化之后 想調用一個重寫的getDuration()方法，有什么辦法么？在不引入子類繼承的前提下。

問題解答

java不能怎么做，但能用內部類變相的實現這個需求

public abstract class Rhythm { /** * @return duration between {@linkplain Note} in milliseconds */ public abstract long getDuration();public abstract class InnderClass {public abstract long getDuration(); } private InnderClass innderClass; public Rhythm() {innderClass = new InnderClass() { @Override public long getDuration() {return Rhythm.this.getDuration(); }}; } public void setInnderClass(InnderClass innderClass) {this.innderClass = innderClass; } public void perform() {long duration = innderClass.getDuration();try { Thread.sleep(duration);} catch (InterruptedException ie) { Thread.currentThread().interrupt(); throw new RuntimeException(ie);} }}

@Override public void play(Rhythm rhythm, Note note, NoteCallback noteCallback){//rhythm.getDuration();//想在這里重寫getDuration方法，如何做到？rhythm.setInnderClass(rhythm.new InnderClass() {@Override public long getDuration() {// TODO 把實現放到這里return 0; }});rhythm.perform();note.getNoteValue();noteCallback.notePlayed(note); }回答2：

做不了吧，如果能做Java豈不是動態語言了？