This answer is based on Eclipse 3.4, but should work in older versions of Eclipse.
When selecting Run As..., go into the run configurations.
On the Arguments tab of your Java run configuration, configure the variable ${string_prompt} to appear (you can click variables to get it, or copy that to set it directly).
Every time you use that run configuration (name it well so you have it for later), you will be prompted for the command line arguments.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…