In this post, We will learn a couple of ways to check if String is number in java?
- The First approach uses regular Expression [-+]?\\d*\\.?\\d+ to check whether input string represents number or not.
- The second approach uses method parseDouble(InputString) from Double class if the input String successfully parse into a number then input String is number otherwise Double.parseDouble(InputString) will throw NumberFormatException then input string is not a number
CheckStringIsNumberOrNotUtil.java
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package com.kkjavatutorials.client; public class CheckStringIsNumberOrNotUtil { public static boolean isNumber1(String inputString) { return inputString != null && inputString.matches("[-+]?\\d*\\.?\\d+"); } public static boolean isNumber2(String inputString) { if (inputString == null || inputString.length() == 0) { return false; } try { Double.parseDouble(inputString); return true; } catch (NumberFormatException e) { return false; } } } |
Client program CheckStringIsNumberOrNot.java
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package com.kkjavatutorials.client; public class CheckStringIsNumberOrNot { public static void main(String[] args) { System.out.println("---Testing Method CheckStringIsNumberOrNotUtil.isNumber1(inputStr)---"); System.out.println("123 is Number:"+CheckStringIsNumberOrNotUtil.isNumber1("123")); System.out.println("45.92 is Number: "+CheckStringIsNumberOrNotUtil.isNumber1("45.92")); System.out.println("xy12 is Number: "+CheckStringIsNumberOrNotUtil.isNumber1("xy12")); System.out.println("-701 is Number: "+CheckStringIsNumberOrNotUtil.isNumber1("-701")); System.out.println("---Testing Method CheckStringIsNumberOrNotUtil.isNumber2(inputStr)---"); System.out.println("123 is Number:"+CheckStringIsNumberOrNotUtil.isNumber2("123")); System.out.println("45.92 is Number: "+CheckStringIsNumberOrNotUtil.isNumber2("45.92")); System.out.println("xy12 is Number: "+CheckStringIsNumberOrNotUtil.isNumber2("xy12")); System.out.println("-701 is Number: "+CheckStringIsNumberOrNotUtil.isNumber2("-701")); } } |
Output of this program:
—Testing Method CheckStringIsNumberOrNotUtil.isNumber1(inputStr)—
123 is Number:true
45.92 is Number: true
xy12 is Number: false
-701 is Number: true
—Testing Method CheckStringIsNumberOrNotUtil.isNumber2(inputStr)—
123 is Number:true
45.92 is Number: true
xy12 is Number: false
-701 is Number: true
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That’s all about How to check if String is number in java?
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