CODEWITHSUNDEEP
javastring
user1005253
user1005253

Reputation: 404

Doing minus operation on string

I have a small problem with the minus operation in java. When the user press the 'backspace' key, I want the char the user typed, to be taken away from the word which exists. e.g word = myname and after one backspace word = mynam

This is kinda of what I have:

String sentence = "";
char c = evt.getKeyChar();
if(c == '\b') {
  sentence = sentence - c;
} else {
  sentence = sentence + c;
}

The add operation works. So if I add a letter, it adds to the existing word. However, the minus isn't working. Am I missing something here? Or doing it completely wrong?

Upvotes: 14

Views: 74854

Answers (4)

Ry-
Ry-

Reputation: 224905

Strings don’t have any kind of character subtraction that corresponds to concatenation with the + operator. You need to take a substring from the start of the string to one before the end, instead; that’s the entire string except for the last character. So:

sentence = sentence.substring(0, sentence.length() - 1);

Upvotes: 15

Moishe Lettvin
Moishe Lettvin

Reputation: 8471

You should investigate the StringBuilder class, eg:

StringBuilder sentence = new StringBuilder();

Then you can do something like:

sentence.append(a);

for a new character or

sentence.deleteCharAt(sentence.length() - 1);

Then when you actually want to use the string, use:

String s = sentence.toString();

Upvotes: 0

Shaun
Shaun

Reputation: 2476

sentance = sentance.substring(0, sentance.length() - 1);

There is no corresponding operator to + which allows you to delete a character from a String.

Upvotes: 0

Andy Thomas
Andy Thomas

Reputation: 86391

For convenience, Java supports string concatenation with the '+' sign. This is the one binary operator with a class type as an operand. See String concatenation operator in the Java Language Specification.

Java does not support an overload of the '-' operator between a String and a char.

Instead, you can remove a character from a string by adding the substrings before and after.

Upvotes: 1

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