From a63c30f5fe9ee302e73bb30e35095d789adb1a80 Mon Sep 17 00:00:00 2001
From: bjculkin <bjculkin@mix.wvu.edu>
Date: Fri, 17 Mar 2017 08:33:37 -0400
Subject: Refactor StringUtils

Moved a bunch of token-oriented stuff from StringUtils to a new TokenUtils
class.
---
 .../java/bjc/utils/parserutils/DoubleMatcher.java  | 71 ++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 BJC-Utils2/src/main/java/bjc/utils/parserutils/DoubleMatcher.java

(limited to 'BJC-Utils2/src/main/java/bjc/utils/parserutils/DoubleMatcher.java')

diff --git a/BJC-Utils2/src/main/java/bjc/utils/parserutils/DoubleMatcher.java b/BJC-Utils2/src/main/java/bjc/utils/parserutils/DoubleMatcher.java
new file mode 100644
index 0000000..63eabca
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/parserutils/DoubleMatcher.java
@@ -0,0 +1,71 @@
+package bjc.utils.parserutils;
+
+import java.util.regex.Pattern;
+
+/*
+ * Checks if a string would pass Double.parseDouble.
+ *
+ * Uses a regex from the javadoc for Double.valueOf()
+ */
+class DoubleMatcher {
+	private static final String	Digits		= "(\\p{Digit}+)";
+	private static final String	HexDigits	= "(\\p{XDigit}+)";
+
+	/*
+	 * an exponent is 'e' or 'E' followed by an optionally signed decimal
+	 * integer.
+	 */
+	private static final String Exp = "[eE][+-]?" + Digits;
+
+	private static final String fpRegex = 
+		"[\\x00-\\x20]*" // Optional  leading  "whitespace"
+		+ "[+-]?(" + // Optional sign character
+		"NaN|" + // "NaN" string
+		"Infinity|" + // "Infinity" string
+
+		/*
+		 * A decimal floating-point string representing a finite
+		 * positive number without a leading sign has at most
+		 * five basic pieces: Digits . Digits ExponentPart
+		 * FloatTypeSuffix
+		 *
+		 * Since this method allows integer-only strings as
+		 * input in addition to strings of floating-point
+		 * literals, the two sub-patterns below are
+		 * simplifications of the grammar productions from
+		 * section 3.10.2 of The Java™ Language Specification.
+		 */
+
+		/*
+		 * Digits ._opt Digits_opt ExponentPart_opt
+		 * FloatTypeSuffix_opt
+		 */
+		"(((" + Digits + "(\\.)?(" + Digits + "?)(" + Exp + ")?)|" +
+
+		/*
+		 * . Digits ExponentPart_opt FloatTypeSuffix_opt
+		 */
+		"(\\.(" + Digits + ")(" + Exp + ")?)|" +
+
+		/*
+		 * Hexadecimal strings
+		 */
+		"((" +
+		/*
+		 * 0[xX] HexDigits ._opt BinaryExponent
+		 * FloatTypeSuffix_opt
+		 */
+		"(0[xX]" + HexDigits + "(\\.)?)|" +
+
+		/*
+		 * 0[xX] HexDigits_opt . HexDigits BinaryExponent
+		 * FloatTypeSuffix_opt
+		 */
+		"(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
+
+		")[pP][+-]?" + Digits + "))" + "[fFdD]?))" + "[\\x00-\\x20]*"; // Optional
+	// trailing
+	// "whitespace"
+
+	public static final Pattern floatingLiteral = Pattern.compile("\\A" + fpRegex + "\\Z");
+}
-- 
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