求个java程序，帮下忙，谢谢

把用户输入的句子要是有的单词是小写开头的，要变成大写，然后把标点符号都变成空格
要求输出结果如下

初始的字符串Original string: Three classes, TestFile1, TestFile2, and TestFile3, must be defined before being used in the Test class.

最终修改过的字符串Modified string: Three Classes Testfile1 Testfile2 And Testfile3 Must Be Defined Before Being Used In The Test Class

String modified = "";
String original="Three classes, TestFile1, TestFile2, and TestFile3, must be defined before being used in the Test class.";
original.replaceAll("",",").replaceAll("",".");
String []modified = original.split(" " );
for(int = 0 ;i<modified.lengh-1;i++){
char ch=test.charAt(0);
if(Character.isLowerCase(ch)){ /*如果首字母是小写
ch=Character.toUpperCase(); 将首字母转变成大写*/
}
modified +＝ （ch ＋ modified[i].subString(1) + " ").toString();
}

自己多动手写，然后才能有提高！

我的分析,不管怎样...

先统统把字符串 分割...

然后处理每个单词的首字母...

最后合并

稍后呈上!

import java.util.Scanner;

public class changeString {
public static void main(String args[]){
Scanner s=new Scanner(System.in);
StringBuffer sf=new StringBuffer();
int counter=0;
while(s.hasNext()){
String temp=s.next();