如何用整数替换字符串中的字符？

Question

Say I have the the string: " aab + bab = b " and I want to

• replace all the a characters with the integer 0,
• replace all the b characters with the integer 1

so it will become:

001 + 101 = 1

what would be the easiest way to do this?

so far I parced the equation into three parts:

System.out.println("Enter an Equation of variables");
_inString = _in.nextLine();

    //find the three different parts of the equation
    String _noSpaces = _inString.replaceAll("\\s+","");
    String delims = "[+,=]";
    String[] _tokens = _noSpaces.split(delims);

Answer 1

You can chain replace methods together

String str = " aab + bab = b ";
str = str.replace("a", "0").replace("b", "1");

We require an assignment back to 'str' because str.replace() returns a new String and the original string would be unchanged. [Because String is immutable in Java]

Answer 2

Do you only have binary operands?

Just do

replaceAll("a", "0");
replaceAll("b", "1");

:

Since you want to evaluate your equation, I suggest you used the solution above, then use a java math parser. Several can be found after a quick googling.

My favourite is Javaluator .

Answer 3

If you want to replace single characters with other single characters you can use
replace(char oldChar, char newChar) to avoid regex used in

• replace(CharSequence target, CharSequence replacement) or
• replaceAll(String regex, String replacement)

like

_inString = _inString.replace('a', '0').replace('b', '1');

Answer 4

You could also do this:

String s = aab + bab = b;

int i = 0;
int i2 = 1;

String ii = i + "";
String ii2 = i2 + "";

I use this because say 1 and 0 were not identified. You could setup i and i2 to be changeable if your API/Platform supports it.