如何替换数组中字符串的索引值

Question

i am making a project about turing machine and i am having a problem about the how do i replace a character in an certain index of a string

Example: if i input in the initial tape: stackoverflow then code in the inputArea like write 1 the output should be 1tackoverflow but sadly the output of my code is 11111111111111

I'm trying to get rid of the loop because i know my loop is the problem but how should i do it ?

Here's my code

runButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent ActE){

    String[] iniTape = iTapeArea.getText().split("");


    String[] input = inputArea.getText().split("\n");
    for(int i=0;i<input.length;i++)
    {
        if(input[i].contains("write")==true){
            sub = input[i].substring(6, input[i].length());
             for(int j=0;j<iniTape.length;j++){
        System.out.print(""+iniTape[j].replace(iniTape[j], sub));

            }
        }
    }
}

});

Answer 1

No need to try this hard. You can use

 String str = "stackoverflow";
 System.out.println(str.replace("" + str.charAt(0), "1"));

Out put:

 1tackoverflow

Answer 2

Use replaceAll() method of String class as below

yourString.replaceAll("" + yourString.charAt(index), "1")//index is your index at which you want to replace

""+ is equivalent of doing String.valueOf(yourString.charAt(index))

Answer 3

This might do the trick

 String[] iniTape = iTapeArea.getText().split(""); String sub= null; String temp = null; String[] input = inputArea.getText().split("\\n"); //"test 1\\ntest 2\\ntest 3".split("\\n"); for(int i=0;i<input.length;i++) { if(input[i].contains("write")==true){ sub = input[i].substring(6, input[i].length()); iniTape[i+1] = sub; } } StringBuffer buffer = new StringBuffer(); for(String str : iniTape) { buffer.append(str); } System.out.println(buffer.toString()); 

replace the index value with the required character

Answer 4

I use the replaceFirst(String, String) function of the String class.

public static void main(String[] args) {
    String s = "stackoverflow";
    s = s.replaceFirst("" + s.charAt(0), "1");
    System.out.println(s);
}

Answer 5

If you want to replace a given certain indexes of a string with that number you can do the following

static String str = "stackoverflow";
public static String replaceCharsAt(int ... indices) {
    for (int index : indicies) {
        str = str.replace(str.charAt(i), i+1);
    }
    return str;
}