给人一种@option注释的默认设置，JAVA

Question

@Option(name = "-readFromFolder",usage = "specifies a folder containing files to read") 
    private String folderName; 

现在的工作是在用户指定文件夹-readFromFolder=/home

我希望他们能够说-readFromFolder并设置默认为它的方式看看，比如$ {}的user.home

东西是这样的，但我ca't找出语法

@Option(name = "-readFromFolder",usage = "specifies a folder containing files to read") 
     private String folderName (default=${user.home}); 

Answer 1

我假设你正在使用args4j库 - 它不支持默认参数值。你必须自己实现：

private final static String DEFAULT_FOLDER_NAME = "${user.home}"; 
@Option(name = "-readFromFolder",usage = "specifies a folder containing files to read") 
private String folderName; 

public String getFolderName() { 
    return null == folderName ? DEFAULT_FOLDER_NAME : folderName ; 
}