Add java code for LCS

动态规划系列/最长公共子序列.md

@@ -147,4 +147,29 @@ else:
 <img src="../pictures/qrcode.jpg" width=200 >
 </p>
 
-======其他语言代码======
+======其他语言代码======
+
+[Shawn](https://github.com/Shawn-Hx) 提供 Java 代码：
+
+```java
+public int longestCommonSubsequence(String text1, String text2) {
+	// 字符串转为char数组以加快访问速度
+	char[] str1 = text1.toCharArray();
+	char[] str2 = text2.toCharArray();
+
+	int m = str1.length, n = str2.length;
+	// 构建dp table，初始值默认为0
+	int[][] dp = new int[m + 1][n + 1];
+	// 状态转移
+	for (int i = 1; i <= m; i++)
+		for (int j = 1; j <= n; j++)
+			if (str1[i - 1] == str2[j - 1])
+				// 找到LCS中的字符
+				dp[i][j] = dp[i-1][j-1] + 1;
+			else
+				dp[i][j] = Math.max(dp[i-1][j], dp[i][j-1]);
+
+	return dp[m][n];
+}
+```
+