返回正确的枚举，而不使用if [英] Return correct enum without using if

问题描述

如果有以下情况，我有任务要更改：

  if（userDecision.equalsIgnoreCase（D））{
 return DirectoriesActivity.DELETE; 
} else if（userDecision.equalsIgnoreCase（R））{
 return DirectoriesActivity.REPLACE; 
} else {
 return DirectoriesActivity.ADD_NEW_CONTENTS; 
} 
  

对于什么会返回只是枚举而不使用if。我必须使用一些枚举属性，但我不知道哪一个：/这是我的枚举：

  public enum DirectoriesActivity { 
 DELETE，
 REPLACE，
 ADD_NEW_CONTENTS; 
} 
  

我尝试这样做：

  public enum DirectoriesActivity {
 DELETE（D），
 REPLACE（R），
 ADD_NEW_CONTENTS（A ）; 
 
 private String directoriesActivityCode; 
 private DirectoriesActivity（String directoriesActivityCode）{
 this.directoriesActivityCode = directoriesActivityCode; 
} 
 
 public DirectoriesActivity getEnum（String x）{
 //不知道该怎么做
} 
} 
 
解决方案
 
这样做：
  public enum DirectoriesActivity {
 DELETE（D），
 REPLACE（R），
 ADD_NEW_CONTENTS（A）; 
 
 private String directoriesActivityCode; 
 
 private DirectoriesActivity（String directoriesActivityCode）{
 this.directoriesActivityCode = directoriesActivityCode; 
} 
 
 public DirectoriesActivity getEnum（String x）{
 for（DirectoriesActivity directoriesActivity：values（））{
 if（directoriesActivity.directoriesActivityCode.equals（x）） {
 return directoriesActivity; 
} 
} 
抛出新的IllegalArgumentException（未知值+ x）; 
} 
} 
  
或者如果您使用Java 8 
  return Arrays.stream（DirectoriesActivity.values（））
 .filter（directoriesActivity  - > directoriesActivity.directoriesActivityCode.equals（userDecision ））
 .findFirst（）
 .orElseThrow（（） - > new IllegalArgumentException（Unknown value+ userDecision））; 
  
 重要的备注这里是这个解决方案比彼得提供的解决方案。但是，只要性能不成问题，我宁愿采用这样的解决方案。
 
I have task to change this if:
if (userDecision.equalsIgnoreCase("D")) {
    return DirectoriesActivity.DELETE;
} else if (userDecision.equalsIgnoreCase("R")) {
    return DirectoriesActivity.REPLACE;
} else {
    return DirectoriesActivity.ADD_NEW_CONTENTS;
}
On something what will return just enum without using if. I have to use some enum properties but I don't know which one :/ Here is my enum:
public enum DirectoriesActivity {
    DELETE,
    REPLACE,
    ADD_NEW_CONTENTS;
}
I tried to do something like this:
public enum DirectoriesActivity {
    DELETE ("D"),
    REPLACE ("R"),
    ADD_NEW_CONTENTS ("A");

    private String directoriesActivityCode;
    private DirectoriesActivity(String directoriesActivityCode)    {
        this.directoriesActivityCode = directoriesActivityCode;
    }

    public DirectoriesActivity getEnum(String x){
        //no idea what to do here
    }
}
Or maybe somebody have some other idea?
解决方案
How about this:
public enum DirectoriesActivity {
    DELETE ("D"),
    REPLACE ("R"),
    ADD_NEW_CONTENTS ("A");

    private String directoriesActivityCode;

    private DirectoriesActivity(String directoriesActivityCode)    {
        this.directoriesActivityCode = directoriesActivityCode;
    }    

    public DirectoriesActivity getEnum(String x){
        for (DirectoriesActivity directoriesActivity : values()) {
            if (directoriesActivity.directoriesActivityCode.equals(x)) {
                return directoriesActivity;
            }
        }
        throw new IllegalArgumentException("Unknown value " + x);
    }
}    
Or in case you are using Java 8
return Arrays.stream(DirectoriesActivity.values())
            .filter(directoriesActivity -> directoriesActivity.directoriesActivityCode.equals(userDecision))
            .findFirst()
            .orElseThrow(() -> new IllegalArgumentException("Unknown value " + userDecision));
Important side note here is that this solution is performing a lot worse than the solution provided by Peter.  But as long as performance is not an issue, I'd prefer a solution like this.

                        
这篇关于返回正确的枚举，而不使用if的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！