替换String中字符的所有实例

Question

I'm trying to create a method that replace all instances of a certain character in a word with a new character. This is what I have so far:

public class practice {
public static void main(String[] args) {

    String test3 = updatePartialword("----", "test", 't');
    System.out.println(test3); }


public static String updatePartialword(String partial, String secret, char c) {
    String newPartial = "";
    int len = secret.length();
    for (int i=0; i<=secret.length()-1; i++){
        char x = secret.charAt(i);
        if (c==x) {
            String first = partial.substring(0,i);
            String second = partial.substring(i+1,len);
            newPartial = first+x+second;
        }


    }
        return newPartial;
}

}

I want it to return t--t, but it will only print the last t. Any help would be greatly appreciated!

Answer 1

Java already has a built in method in String for this. You can use the the replace() method to replace all occurrences of the given character in the String with the another character

    String str = "Hello";
    str.replace('l', '-'); //Returns He--o
    str.replace('H', '-'); //Returns -ello

Answer 2

I suspect you are looking for something like

public static void main(String[] args) {
    String test3 = updatePartialword("----", "test", 't');
    System.out.println(test3);
}

public static String updatePartialword(String partial, String secret, char c) {
    char[] tmp = partial.toCharArray();

    for (int i = 0; i < secret.length(); i++) {
        char x = secret.charAt(i);
        if (c == x) {
            tmp[i] = c;
        }

    }
    return new String(tmp);
}

Answer 3

In your code you overwrite the String each time you found the character. Instead of overwriting, you should expand the string each time.

public class practice {
  public static void main(String[] args) {
    String test3 = updatePartialword("----", "test", 't');
    System.out.println(test3); 
}

public static String updatePartialword(String partial, String secret, char c) {
    StringBuilder sb = new Stringbuilder();
    sb.append(""); // to prevent the Stringbuilder from calculating with the chars
    for (int i = 0; i < partial.lenght; i++)
      if (secret.charAt(i) == c)
        sb.append(c);
      else
        sb.append('-');
    return sb.toString();
  }

}