string compare ignore case done

Author: Ram swaroop

src/me/ramswaroop/bits/StrCmp.java

@@ -0,0 +1,78 @@
+package me.ramswaroop.bits;
+
+/**
+ * Created by IntelliJ IDEA.
+ *
+ * @author: ramswaroop
+ * @date: 6/15/15
+ * @time: 10:38 AM
+ */
+public class StrCmp {
+
+    /**
+     * Compares two strings {@param s1} and {@param s2} lexicographically ignoring case.
+     * If both are equal, it returns 0 otherwise their lexicographic differences.
+     *
+     * @param s1
+     * @param s2
+     * @return
+     */
+    public static int compareStringIgnoreCase(String s1, String s2) {
+        int n1 = s1.length();
+        int n2 = s2.length();
+        int min = Math.min(n1, n2);
+        for (int i = 0; i < min; i++) {
+            char c1 = s1.charAt(i);
+            char c2 = s2.charAt(i);
+            if (c1 != c2) {
+                // If characters don't match but case may be ignored,
+                // try converting both characters to uppercase.
+                // If the results match, then the comparison scan should
+                // continue.
+                c1 = Character.toUpperCase(c1);
+                c2 = Character.toUpperCase(c2);
+                if (c1 != c2) {
+                    // Unfortunately, conversion to uppercase does not work properly
+                    // for the Georgian alphabet, which has strange rules about case
+                    // conversion. So we need to make one last check before
+                    // exiting.
+                    c1 = Character.toUpperCase(c1);
+                    c2 = Character.toUpperCase(c2);
+                    if (c1 != c2) {
+                        // No overflow because of numeric promotion
+                        return c1 - c2;
+                    }
+                }
+            }
+        }
+        return n1 - n2;
+    }
+
+    public static void main(String a[]) {
+        System.out.println(compareStringIgnoreCase("ram", "ram"));
+        System.out.println(compareStringIgnoreCase("ram", "Ram"));
+        System.out.println(compareStringIgnoreCase("", ""));
+        System.out.println(compareStringIgnoreCase("", " "));
+        System.out.println(compareStringIgnoreCase(" ", " "));
+        System.out.println(compareStringIgnoreCase(" ", ""));
+        System.out.println(compareStringIgnoreCase("Geeks", "apple"));
+        System.out.println(compareStringIgnoreCase("", "ABCD"));
+        System.out.println(compareStringIgnoreCase("ABCD", "z"));
+        System.out.println(compareStringIgnoreCase("ABCD", "abcdEghe"));
+        System.out.println(compareStringIgnoreCase("GeeksForGeeks", "gEEksFORGeEKs"));
+        System.out.println(compareStringIgnoreCase("GeeksForGeeks", "geeksForGeeks"));
+        System.out.println("--------------------");
+        System.out.println("ram".compareToIgnoreCase("ram"));
+        System.out.println("ram".compareToIgnoreCase("Ram"));
+        System.out.println("".compareToIgnoreCase(""));
+        System.out.println("".compareToIgnoreCase(" "));
+        System.out.println(" ".compareToIgnoreCase(" "));
+        System.out.println(" ".compareToIgnoreCase(""));
+        System.out.println("Geeks".compareToIgnoreCase("apple"));
+        System.out.println("".compareToIgnoreCase("ABCD"));
+        System.out.println("ABCD".compareToIgnoreCase("z"));
+        System.out.println("ABCD".compareToIgnoreCase("abcdEghe"));
+        System.out.println("GeeksForGeeks".compareToIgnoreCase("gEEksFORGeEKs"));
+        System.out.println("GeeksForGeeks".compareToIgnoreCase("geeksForGeeks"));
+    }
+}