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【Java】Regular Expression Pattern

判斷正負實數 

• [+-]?((\d+\.?\d*)|(\.\d+))
• https://regex101.com/r/zB7vV3/27

String pattern = "[+-]?((\\d+\\.?\\d*)|(\\.\\d+))";
// Create a Pattern objectPattern r = Pattern.compile(pattern);// Now create matcher object.Matcher m = r.matcher(expression);int x = 0;while (m.find()) {
    Log.d("[FIND]", x + ":-->" + m.group(x++));}

return m.find();

判斷整數加減乘除

• ^(\d+[\+\-\*\/]{1})+\d+$
• https://regex101.com/r/zB7vV3/28

規則

• http://ccckmit.wikidot.com/regularexpression

移除開頭多餘0

expression.replaceAll("^(0+)", "");

或

expression.replaceFirst("^0+", "")