public class splitstr {
   
    public static void main(String args[])
    {
    String oldstr="I am a programmer";
    String[] str = oldstr.split(" ");
    String finalstr="";
    for(int i=str.length-1;i>-1;i--)
    {
      finalstr=finalstr+str[i]+" ";
    }
    System.out.println(finalstr);
    }
}

public class tts {
   
    public static void main(String args[])
    {
    String oldstr="I am  a   programmer";
    String[] str = oldstr.split(" ");
    String finalstr="";
    for(int i=str.length-1;i>-1;i--)
    {   
      if(str[i].equalsIgnoreCase(""))
      {
         continue;
      }
      if(i==0)
      {
          finalstr=finalstr+str[i].trim();
          continue;
      } 
      finalstr=finalstr+str[i].trim()+" ";
    }
    System.out.println(finalstr);
    }
}

String str = "i am  a   test";

    StringBuilder out = new StringBuilder(str.length());
    StringBuilder field = new StringBuilder();
   
    char[] charArray = str.toCharArray();
   
    for(int i = charArray.length - 1; i >= 0; i --) {
       
        if(charArray[i] != ' '){
            field.insert(0, charArray[i]);
           
        } else {
            if(field.length() != 0) {
                out.append(field.toString()) ;
                field = new StringBuilder();
            }
            out.append(" ");
        }
    }
   
    if(field.length() != 0) out.append(field.toString());
    System.out.println(out.toString());

int i = 0;
String oldstr=" I am  a   programmer";
int length = oldstr.length();

List<String> list = new ArrayList<String>();
//这是以空格开头的情况
if(oldstr.substring(0, 1).equals(" ")) {
    String space = "";
    int temp = 0;
    for(int m = i; m < length; m++) {
        if(oldstr.codePointAt(m) != 32) {
            temp = m;
            break;
        }
    }
    space = oldstr.substring(i, temp);
    list.add(space);
    i = temp;
}
while(i < length) {
    //获取空格之间的单词
    int temp = 0;
    Boolean bool = false;
    String word = "";
    for(int m = i; m < length; m++) {
        if(oldstr.codePointAt(m) == 32) {
            temp = m;
            bool = true;
            break;
        }
    }
    if(!bool) {//说明是截取到oldstr的结尾
        temp = length;
    }
    word = oldstr.substring(i, temp);
    list.add(word);
    i = temp;
    bool = false;
    //获取单词之间的空格
    if(i < length) {
        String space = "";
            for(int m = i; m < length; m++) {
                     if(oldstr.codePointAt(m) != 32) {
                temp = m;
                bool = true;
                break;
            }
        }
        if(!bool) {
            temp = length;
        }
        space = oldstr.substring(i, temp);
        list.add(space);
        i = temp;
    }
}
String newstr = "";
for(int j = list.size() - 1; j >= 0; j--) {
    newstr += list.get(j);
}
System.out.println(newstr);

public class StringTest {
    private static String convert(String str) {
        if (str == null) {
            return null;
        }

        char[] cs = str.toCharArray();
        char[] cs0 = new char[cs.length];
        int temp = cs.length;
       
        for (int start = 0; start < cs.length;) {
            boolean isBlank = isBlank(cs[start]);
            int end = start;
            for (; end < cs.length; end++) {
                if (isBlank != isBlank(cs[end])) {
                    break;
                }
            }
            System.arraycopy(cs, start, cs0, temp - (end - start),
                    (end - start));
            temp -= (end - start);
            start = end;
        }
        return String.valueOf(cs0);
    }

    private static boolean isBlank(char c) {
        return c == ' ';
    }

    public static void main(String[] args) {
        System.out.println(convert("1"));
    }
}

String oldstr=" I am  a   programmer ";
List<String> list = new ArrayList<String>();
String regEx1 = "[a-zA-Z]+";
String regEx2 = " +";
Pattern p1 = Pattern.compile(regEx1);
Pattern p2 = Pattern.compile(regEx2);
Matcher m = Pattern.compile("^ +").matcher(oldstr);
if(m.find()) {
    list.add(m.group());
    oldstr = m.replaceAll("");
}
while(oldstr.length() > 0) {
    Matcher m1 = p1.matcher(oldstr);
    if(m1.find()) {
        list.add(m1.group());
        oldstr = m1.replaceFirst("");   
    }
    Matcher m2 = p2.matcher(oldstr);
    if(oldstr.length() > 0 && m2.find()) {
        list.add(m2.group());
        oldstr = m2.replaceFirst("");
    }           
}
String newstr = "";
for(int j = list.size() - 1; j >= 0; j--) {
    newstr += list.get(j);
}
System.out.println(newstr);

public class Test {

    public static void main(String[] args) {
        String str = "I am  a   programmer";
        char[] chs = str.toCharArray();
        for(int i = 0, offset = 0; i < chs.length; i++) {
            char h = chs[chs.length - 1];
            if(h == ' ') {
                offset = i;
            }
            for(int j = chs.length - 2; j >= offset; j--) {
                chs[j + 1] = chs[j];
            }
            if(h == ' ') {
                chs[i] = h;
                offset++;
            } else {
                chs[offset] = h;
            }
        }
        System.out.println(chs);
    }
}