有两种方法可以实现，一种是使用jni调c程序(这个我还没试过),另一种就是纯java的实现方式(不过可能会有点闪烁).
原理很简单，就是另外启动一个线程，不停的写提示输入密码，而主线程负责读密码.


public class CTest implements Runnable
{
Thread thread = null;
public boolean flag = false;
 
public static void main(String s[])
{
try
{
StringBuffer password = new StringBuffer();
CTest c = new CTest();
c.test();

while(true)
{ 
char cc = (char)System.in.read();
c.flag = true;
if(cc != '\r' && cc != '\n')
{
password.append(cc);
}

if(cc == '\n')
{
break;
}
}
System.out.println("Your password is:" + password.toString());
}
catch(Exception e )
{
 System.out.println(e);
} 
}

public void run()
{
while(!flag)
{
 try
 {
 System.out.print("\r" + "Please enter your password:" + " \r" );
 thread.sleep(10);
 }
 catch(Exception e)
 {}
}
}

public void test() throws Exception
{
 if(thread==null)
{
 thread=new Thread(this);
 thread.start(); 
}
}

}