Setting a StringBuilder

Question

I have 3 buttons: "Q", "W" and "E". When clicked they should append their letter to a StringBuilder. Like this:

StringBuilder s = new StringBuilder();

(When "Q" button is clicked):

s.append("q");

(When "W" button clicked):

s.append("w");

But what I want is to have a maximum of 3 characters to be in the StringBuilder. 3 digits after reaching the initial character of a key is pressed at the end wiper and write a new one. After the StringBuilder reaches three characters, it will remove the initial one and append the next. Like marquee. Example:

StringBuilder is "QWW",
When E button clicked StringBuilder must be "WWE".
When W button clicked StringBuilder must be "WEW".

@MarounMaroun lol..Me too.. So Erkan what have you tried...? — Vishal K
– Vishal K, Commented Mar 30, 2013 at 20:52
Adding to @MarounMaroun, do you have sample code you have written so that we can help you fix this problem? — justderb
– justderb, Commented Mar 30, 2013 at 20:52
Maybe you don't want a StringBuilder, but a circular buffer? — NilsH
– NilsH, Commented Mar 30, 2013 at 20:54
Agree with @NilsH, this isn't StringBuilder, what you want is more of a character Queue. — Taylor
– Taylor, Commented Mar 30, 2013 at 20:56

gkiko · Accepted Answer · 2013-03-30 21:01:18Z

1

The alternative way is to use char array

char[] arr = new char[]{'','',''};
...
private void appendChar(char a){
  for(int i=0;i<arr.length-1;i++){
    arr[i] = arr[i+1];
  }
  arr[arr.length-1] = a;
}

And finally:

String res = new String(arr);

answered Mar 30, 2013 at 21:01

gkiko

2,2873 gold badges31 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Eng.Fouad · Accepted Answer · 2013-03-30 20:57:05Z

0

Use StringBuilder#deleteCharAt(int index):

public static void addToStringBuilder(StringBuilder sb, int max, char letter)
{
    if(sb.length() >= max) sb.deleteCharAt(0);
    sb.append(letter);
}

For example:

StringBuilder sb = new StringBuilder();
addToStringBuilder(sb, 3, 'Q');
System.out.println(sb);
addToStringBuilder(sb, 3, 'W');
System.out.println(sb);
addToStringBuilder(sb, 3, 'W');
System.out.println(sb);
addToStringBuilder(sb, 3, 'E');
System.out.println(sb);
addToStringBuilder(sb, 3, 'W');
System.out.println(sb);

OUTPUT:

Q
QW
QWW
WWE
WEW

answered Mar 30, 2013 at 20:57

Eng.Fouad

118k75 gold badges326 silver badges431 bronze badges

Comments

Vishal K · Accepted Answer · 2013-03-30 20:58:51Z

0

Here you go:

StringBuilder sBuilder = new StringBuilder();
public void prepareBuilder(String str)
{
  if (sBuilder.length() < 3)
  sBuilder.append(str);
  else 
  {
    sBuilder.deleteCharAt(0);
    sBuilder.append(str);

  }
}

answered Mar 30, 2013 at 20:58

Vishal K

13.1k2 gold badges30 silver badges38 bronze badges

Collectives™ on Stack Overflow

Setting a StringBuilder

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related