encode and decode strings solution

Author: yhkee0404

encode-and-decode-strings/yhkee0404.java

@@ -0,0 +1,44 @@
+public class Solution {
+    /*
+     * @param strs: a list of strings
+     * @return: encodes a list of strings to a single string.
+     */
+    public String encode(List<String> strs) {
+        // write your code here
+        return strs.parallelStream()
+                .map(s ->
+                    s.chars()
+                            .parallel()
+                            .mapToObj(c -> new StringBuilder(String.format("%02x", c)))
+                            .collect(
+                                StringBuilder::new,
+                                StringBuilder::append,
+                                (a, b) -> a.append(b)
+                            )
+                ).collect(
+                    StringBuilder::new,
+                    (a, b) -> a.append(b)
+                            .append(' '),
+                    (a, b) -> a.append(b)
+                ).toString();
+    }
+
+    /*
+     * @param str: A string
+     * @return: decodes a single string to a list of strings
+     */
+    public List<String> decode(String str) {
+        // write your code here
+        final List<String> ans = new ArrayList<>();
+        final StringTokenizer st = new StringTokenizer(str);
+        while (st.hasMoreTokens()) {
+            final String s = st.nextToken();
+            final StringBuilder sb = new StringBuilder();
+            for (int i = 0; i < s.length(); i += 2) {
+                sb.append((char) Integer.parseInt(s.substring(i, i + 2), 16));
+            }
+            ans.add(sb.toString());
+        }
+        return ans;
+    }
+}