替换空格

No.4

public class Example {
public static void main(String args[]){
String s = "Hello World!";
System.out.print(replaceSpace(s));
}
public static String replaceSpace(String s){
if(s==null)
return null;
StringBuffer sb = new StringBuffer();
for(int i = 0;i < s.length();i++){
if(s.charAt(i)!=' '){
sb.append(String.valueOf(s.charAt(i)));
}
else{
sb.append("%20");
}
}
return new String(sb);
}
}