Determine if a string is numeric: Difference between revisions
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=={{header|Java}}== |
=={{header|Java}}== |
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<syntaxhighlight lang="java"> |
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public static void main(String[] args) { |
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String value; |
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value = "1234567"; |
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System.out.printf("%-10s %b%n", value, isInteger(value)); |
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value = "12345abc"; |
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System.out.printf("%-10s %b%n", value, isInteger(value)); |
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value = "-123.456"; |
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System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); |
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value = "-.456"; |
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System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); |
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value = "123."; |
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System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); |
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value = "123.abc"; |
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System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); |
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} |
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static boolean isInteger(String string) { |
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String digits = "0123456789"; |
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for (char character : string.toCharArray()) { |
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if (!digits.contains(String.valueOf(character))) |
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return false; |
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} |
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return true; |
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} |
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static boolean isFloatingPoint(String string) { |
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/* at least one decimal-point */ |
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int indexOf = string.indexOf('.'); |
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if (indexOf == -1) |
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return false; |
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/* assure only 1 decimal-point */ |
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if (indexOf != string.lastIndexOf('.')) |
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return false; |
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if (string.charAt(0) == '-' || string.charAt(0) == '+') { |
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string = string.substring(1); |
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indexOf--; |
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} |
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String integer = string.substring(0, indexOf); |
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if (!integer.isEmpty()) { |
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if (!isInteger(integer)) |
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return false; |
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} |
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String decimal = string.substring(indexOf + 1); |
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if (!decimal.isEmpty()) |
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return isInteger(decimal); |
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return true; |
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} |
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</syntaxhighlight> |
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<pre> |
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1234567 true |
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12345abc false |
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-123.456 true |
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-.456 true |
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123. true |
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123.abc false |
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</pre> |
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<br /> |
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It's generally bad practice in Java to rely on an exception being thrown since exception handling is relatively expensive. If non-numeric strings are common, you're going to see a huge performance hit. |
It's generally bad practice in Java to rely on an exception being thrown since exception handling is relatively expensive. If non-numeric strings are common, you're going to see a huge performance hit. |
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<syntaxhighlight lang="java">public boolean isNumeric(String input) { |
<syntaxhighlight lang="java">public boolean isNumeric(String input) { |
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