[5기 최정은] Shorten-URL 과제 제출합니다.

src/main/java/com/springboot/springbooturlshortner/util/Base62Util.java

@@ -0,0 +1,30 @@
+package com.springboot.springbooturlshortner.util;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Base62Util {
+
+    private final String BASE62_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+    private final int BASE62_CHARS_SIZE = 62;
+
+    public String encoding(long urlId) {
+        StringBuffer sb = new StringBuffer();
+        int charactersLength = BASE62_CHARS.length();
+        while (urlId > 0) {
+            sb.append(BASE62_CHARS.charAt((int) (urlId % charactersLength)));
+            urlId /= BASE62_CHARS_SIZE;
+        }
+        return sb.toString();
+    }
+
+    public long decoding(String uniqueKey) {
+        long urlId = 0, power = 1;
+        for (int i = 0; i < uniqueKey.length(); i++) {
+            urlId += BASE62_CHARS.indexOf(uniqueKey.charAt(i)) * power;
+            power *= BASE62_CHARS_SIZE;
+        }
+        return urlId;
+    }
+
+}