判断最后的字符是不是possible
1，判断最后的字符是不是possible, 用endswith方法，接下来再替换
2，替换最后一个可以变项的作

String s = "The possible problem is, How is that possible";
if(s.endsWith("possible")){
String s1 = s.substring(0, s.lastIndexOf("possible"));
s = s1 + "impossible";
}
System.out.println(s);