public static String setProperty(String key, String value) {

checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new PropertyPermission(key, SecurityConstants.PROPERTY_WRITE_ACTION)); }

return (String) props.setProperty(key, value);

}

这个方法应该是往虚拟机这个大容器里添加变量值。