打印字符串中的字符（第一个字符；然后是第一个和第二个；然后是第一个，第二个和第三个）

Question

In java, if I wanted to print out characters from a string in this order:

String str = "abcdefg";
System.out.println("a");
System.out.println("ab");
System.out.println("abc");
System.out.println("abcd");
System.out.println("abcde");
System.out.println("abcdef");
System.out.println("abcdefg");

Which algorithm can I use to do this?

Answer 1

Here is the code you need:

String str = "abcdefg";
for (int i =1 ;i<str.length();i++){
  System.out.println(str.substring(0,i));
}


For all List elements:

    List<String> list = new ArrayList<String>();
    list.add("abcdefg");
    list.add("hijklm");
    for (String str : list) {
      for (int i =1 ;i<str.length();i++){
        System.out.println(str.substring(0,i));
      }
    }

Answer 2

There are several ways, one would be to use a StringBuilder for example...

String str = "abcdefg";
StringBuilder sb = new StringBuilder(str.length());
for (char c : str.toCharArray()) {
    sb.append(c);
    System.out.println(sb);
}

This simply takes each character in turn and appends it to the StringBuilder and prints the result...as an example ;)