diff --git a/problems/0059.螺旋矩阵II.md b/problems/0059.螺旋矩阵II.md
index 4d5d80f6..22229302 100644
--- a/problems/0059.螺旋矩阵II.md
+++ b/problems/0059.螺旋矩阵II.md
@@ -130,57 +130,37 @@ Java：
 ```Java
 class Solution {
     public int[][] generateMatrix(int n) {
+        int loop = 0;  // 控制循环次数
         int[][] res = new int[n][n];
+        int start = 0;  // 每次循环的开始点(start, start)
+        int count = 1;  // 定义填充数字
+        int i, j;
 
-        // 循环次数
-        int loop = n / 2;
-
-        // 定义每次循环起始位置
-        int startX = 0;
-        int startY = 0;
-
-        // 定义偏移量
-        int offset = 1;
-
-        // 定义填充数字
-        int count = 1;
-
-        // 定义中间位置
-        int mid = n / 2;
-        while (loop > 0) {
-            int i = startX;
-            int j = startY;
-
+        while (loop++ < n / 2) { // 判断边界后，loop从1开始
             // 模拟上侧从左到右
-            for (; j<startY + n -offset; ++j) {
-                res[startX][j] = count++;
+            for (j = start; j < n - loop; j++) {
+                res[start][j] = count++;
             }
 
             // 模拟右侧从上到下
-            for (; i<startX + n -offset; ++i) {
+            for (i = start; i < n - loop; i++) {
                 res[i][j] = count++;
             }
 
             // 模拟下侧从右到左
-            for (; j > startY; j--) {
+            for (; j >= loop; j--) {
                 res[i][j] = count++;
             }
 
             // 模拟左侧从下到上
-            for (; i > startX; i--) {
+            for (; i >= loop; i--) {
                 res[i][j] = count++;
             }
-
-            loop--;
-
-            startX += 1;
-            startY += 1;
-
-            offset += 2;
+            start++;
         }
 
         if (n % 2 == 1) {
-            res[mid][mid] = count;
+            res[start][start] = count;
         }
 
         return res;
diff --git a/problems/0150.逆波兰表达式求值.md b/problems/0150.逆波兰表达式求值.md
index fd3d69aa..6ce7e2f9 100644
--- a/problems/0150.逆波兰表达式求值.md
+++ b/problems/0150.逆波兰表达式求值.md
@@ -136,19 +136,19 @@ java:
 class Solution {
     public int evalRPN(String[] tokens) {
         Deque<Integer> stack = new LinkedList();
-        for (int i = 0; i < tokens.length; ++i) {
-            if ("+".equals(tokens[i])) {        // leetcode 内置jdk的问题，不能使用==判断字符串是否相等
+        for (String s : tokens) {
+            if ("+".equals(s)) {        // leetcode 内置jdk的问题，不能使用==判断字符串是否相等
                 stack.push(stack.pop() + stack.pop());      // 注意 - 和/ 需要特殊处理
-            } else if ("-".equals(tokens[i])) {
+            } else if ("-".equals(s)) {
                 stack.push(-stack.pop() + stack.pop());
-            } else if ("*".equals(tokens[i])) {
+            } else if ("*".equals(s)) {
                 stack.push(stack.pop() * stack.pop());
-            } else if ("/".equals(tokens[i])) {
+            } else if ("/".equals(s)) {
                 int temp1 = stack.pop();
                 int temp2 = stack.pop();
                 stack.push(temp2 / temp1);
             } else {
-                stack.push(Integer.valueOf(tokens[i]));
+                stack.push(Integer.valueOf(s));
             }
         }
         return stack.pop();