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Task/Determine-if-a-string-is-numeric/Mirah/determine-if-a-string-is-numeric.mirah

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+import java.text.NumberFormat
+import java.text.ParsePosition
+import java.util.Scanner
+
+# this first example relies on catching an exception,
+# which is bad style and poorly performing in Java
+def is_numeric?(s:string)
+    begin
+        Double.parseDouble(s)
+        return true
+    rescue
+        return false
+    end
+end
+
+puts '123   is numeric' if is_numeric?('123')
+puts '-123  is numeric' if is_numeric?('-123')
+puts '123.1 is numeric' if is_numeric?('123.1')
+
+puts 'nil   is not numeric' unless is_numeric?(nil)
+puts "''    is not numeric" unless is_numeric?('')
+puts 'abc   is not numeric' unless is_numeric?('abc')
+puts '123-  is not numeric' unless is_numeric?('123-')
+puts '1.2.3 is not numeric' unless is_numeric?('1.2.3')
+
+
+# check every element of the string
+def is_numeric2?(s: string)
+    if (s == nil || s.isEmpty())
+        return false
+    end
+    if (!s.startsWith('-'))
+        if s.contains('-')
+            return false
+        end
+    end
+
+    0.upto(s.length()-1) do |x|
+        c = s.charAt(x)
+        if ((x == 0) && (c == '-'.charAt(0)))
+            # negative number
+        elsif (c == '.'.charAt(0))
+            if (s.indexOf('.', x) > -1)
+                return false # more than one period
+            end
+        elsif (!Character.isDigit(c))
+            return false
+        end
+    end
+    true
+end
+
+
+puts '123   is numeric' if is_numeric2?('123')
+puts '-123  is numeric' if is_numeric2?('-123')
+puts '123.1 is numeric' if is_numeric2?('123.1')
+
+puts 'nil   is not numeric' unless is_numeric2?(nil)
+puts "''    is not numeric" unless is_numeric2?('')
+puts 'abc   is not numeric' unless is_numeric2?('abc')
+puts '123-  is not numeric' unless is_numeric2?('123-')
+puts '1.2.3 is not numeric' unless is_numeric2?('1.2.3')
+
+
+
+# use a regular  expression
+def is_numeric3?(s:string)
+  s == nil || s.matches("[-+]?\\d+(\\.\\d+)?")
+end
+
+puts '123   is numeric' if is_numeric3?('123')
+puts '-123  is numeric' if is_numeric3?('-123')
+puts '123.1 is numeric' if is_numeric3?('123.1')
+
+puts 'nil   is not numeric' unless is_numeric3?(nil)
+puts "''    is not numeric" unless is_numeric3?('')
+puts 'abc   is not numeric' unless is_numeric3?('abc')
+puts '123-  is not numeric' unless is_numeric3?('123-')
+puts '1.2.3 is not numeric' unless is_numeric3?('1.2.3')
+
+
+#  use the positional parser in the java.text.NumberFormat object
+# (a more robust solution). If, after parsing, the parse position is at
+# the end of the string, we can deduce that the entire string was a
+# valid number.
+def is_numeric4?(s:string)
+    return false if s == nil
+    formatter = NumberFormat.getInstance()
+    pos = ParsePosition.new(0)
+    formatter.parse(s, pos)
+    s.length() == pos.getIndex()
+end
+
+
+puts '123   is numeric' if is_numeric4?('123')
+puts '-123  is numeric' if is_numeric4?('-123')
+puts '123.1 is numeric' if is_numeric4?('123.1')
+
+puts 'nil   is not numeric' unless is_numeric4?(nil)
+puts "''    is not numeric" unless is_numeric4?('')
+puts 'abc   is not numeric' unless is_numeric4?('abc')
+puts '123-  is not numeric' unless is_numeric4?('123-')
+puts '1.2.3 is not numeric' unless is_numeric4?('1.2.3')
+
+
+# use the java.util.Scanner object. Very useful if you have to
+# scan multiple entries. Scanner also has similar methods for longs,
+# shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well
+# as methods for integral types where you may input a base/radix other than
+# 10 (10 is the default, which can be changed using the useRadix method).
+def is_numeric5?(s:string)
+    return false if s == nil
+    Scanner sc = Scanner.new(s)
+    sc.hasNextDouble()
+end
+
+puts '123   is numeric' if is_numeric5?('123')
+puts '-123  is numeric' if is_numeric5?('-123')
+puts '123.1 is numeric' if is_numeric5?('123.1')
+
+puts 'nil   is not numeric' unless is_numeric5?(nil)
+puts "''    is not numeric" unless is_numeric5?('')
+puts 'abc   is not numeric' unless is_numeric5?('abc')
+puts '123-  is not numeric' unless is_numeric5?('123-')
+puts '1.2.3 is not numeric' unless is_numeric5?('1.2.3')