42 翻转单词顺序

package question42;

public class ReverseWordsInSentence {
public static String ReverseSentence(String str) {
if(str == null){ return null;}
if(str.trim().equals("")){
return str;
}
String string = str;
String[] strings = string.split(" ");
StringBuilder sBuilder = new StringBuilder();
for (int i = strings.length-1 ; i>=0;i--) {
if(i == 0){
sBuilder.append(strings[i]);
}else {
sBuilder.append(strings[i]);
sBuilder.append(" ");
}
}

String string2 = sBuilder.toString();
return string2;
}

public static void main(String[] args) {
// TODO Auto-generated method stub

String input="I am liu shu xiu";

String a[]=input.split(" ");

for (int i = 0,j=a.length-1; i <j; i++,j--) {
String t=a[i];
a[i]=a[j];
a[j]=t;
}
String output="";
for (int i = 0; i < a.length; i++) {
if (i==a.length-1) {
output=output+a[i];
}else {
output=output+a[i]+" ";
}

}
System.out.println(output);
String res=ReverseSentence(input);
System.out.println(res);
}

private static String doit(String string) {
// TODO Auto-generated method stub
StringBuilder sb=new StringBuilder(string );

return sb.reverse().toString();
}

}