add string to url java solution

lcci/01.03.String to URL/README.md

@@ -41,7 +41,22 @@ class Solution:
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
-
+class Solution {
+    public String replaceSpaces(String S, int length) {
+        char[] c = S.toCharArray();
+        int j = c.length;
+        for (int i = length - 1; i >= 0; i--) {
+            if (c[i] == ' ') {
+                c[--j] = '0';
+                c[--j] = '2';
+                c[--j] = '%';
+            } else {
+                c[--j] = c[i];
+            }
+        }
+        return new String(c, j, c.length - j);
+    }
+}
 ```
 
 ### ...

lcci/01.03.String to URL/README_EN.md

@@ -67,7 +67,22 @@ class Solution:
 ### Java
 
 ```java
-
+class Solution {
+    public String replaceSpaces(String S, int length) {
+        char[] c = S.toCharArray();
+        int j = c.length;
+        for (int i = length - 1; i >= 0; i--) {
+            if (c[i] == ' ') {
+                c[--j] = '0';
+                c[--j] = '2';
+                c[--j] = '%';
+            } else {
+                c[--j] = c[i];
+            }
+        }
+        return new String(c, j, c.length - j);
+    }
+}
 ```
 
 ### ...

lcci/01.03.String to URL/Solution.java

@@ -0,0 +1,16 @@
+class Solution {
+    public String replaceSpaces(String S, int length) {
+        char[] c = S.toCharArray();
+        int j = c.length;
+        for (int i = length - 1; i >= 0; i--) {
+            if (c[i] == ' ') {
+                c[--j] = '0';
+                c[--j] = '2';
+                c[--j] = '%';
+            } else {
+                c[--j] = c[i];
+            }
+        }
+        return new String(c, j, c.length - j);
+    }
+}