add new methods

src/main/java/com/xxl/tool/core/StringTool.java

@@ -7,9 +7,19 @@
  * (some references to other libraries)
  */
 public class StringTool {
+
+    /**
+     * The empty String {@code ""}.
+     */
     public static final String EMPTY = "";
+    /**
+     * Represents a failed index search.
+     */
+    public static final int INDEX_NOT_FOUND = -1;
+
 
     // ---------------------- empty ----------------------
+
     /**
      * is empty
      *
@@ -25,7 +35,7 @@ public class StringTool {
      * @return
      */
     public static boolean isEmpty(String str) {
-        return str == null || str.length() == 0;
+        return str == null || str.isEmpty();
     }
 
     /**
@@ -48,6 +58,7 @@ public static boolean isNotEmpty(String str) {
 
 
     // ---------------------- blank ----------------------
+
     /**
      * is blank
      *
@@ -63,7 +74,7 @@ public static boolean isNotEmpty(String str) {
      * @return
      */
     public static boolean isBlank(String str) {
-        return str == null || str.trim().length()==0;
+        return str == null || str.trim().isEmpty();
     }
 
     /**
@@ -84,7 +95,9 @@ public static boolean isNotBlank(String str) {
         return !StringTool.isBlank(str);
     }
 
+
     // ---------------------- trim ----------------------
+
     /**
      * trim
      *
@@ -140,9 +153,12 @@ public static String trimToEmpty(String str) {
         return str == null ? EMPTY : str.trim();
     }
 
+
     // ---------------------- isNumeric ----------------------
 
     /**
+     * isNumeric
+     *
      * <p>Checks if the String contains only unicode digits.
      * A decimal point is not a unicode digit and returns false.</p>
      *
@@ -177,5 +193,115 @@ public static boolean isNumeric(String str) {
     }
 
 
+    // ---------------------- Count matches ----------------------
+
+    /**
+     * Count matches
+     *
+     * <p>Counts how many times the substring appears in the larger string.</p>
+     *
+     * <p>A {@code null} or empty ("") String input returns {@code 0}.</p>
+     *
+     * <pre>
+     * StringUtils.countMatches(null, *)       = 0
+     * StringUtils.countMatches("", *)         = 0
+     * StringUtils.countMatches("abba", null)  = 0
+     * StringUtils.countMatches("abba", "")    = 0
+     * StringUtils.countMatches("abba", "a")   = 2
+     * StringUtils.countMatches("abba", "ab")  = 1
+     * StringUtils.countMatches("abba", "xxx") = 0
+     * </pre>
+     *
+     * @param str  the CharSequence to check, may be null
+     * @param sub  the substring to count, may be null
+     * @return the number of occurrences, 0 if either CharSequence is {@code null}
+     */
+    public static int countMatches(String str, String sub) {
+        if (isEmpty(str) || isEmpty(sub)) {
+            return 0;
+        }
+        int count = 0;
+        int idx = 0;
+        while ((idx = str.indexOf(sub, idx)) != INDEX_NOT_FOUND) {
+            count++;
+            idx += sub.length();
+        }
+        return count;
+    }
+
+    // ---------------------- Count matches ----------------------
+
+    /**
+     * upperCase first letter
+     *
+     * <pre>
+     *      StringUtils.upperCaseFirst(null, *)     = null
+     *      StringUtils.upperCaseFirst("", *)       = ""
+     *      StringUtils.countMatches("abc", *)      = "Abc"
+     * </pre>
+     *
+     * @param text
+     * @return
+     */
+    public static String upperCaseFirst(String text) {
+        if (isBlank(text)) {
+            return text;
+        }
+        return text.substring(0, 1).toUpperCase() + text.substring(1);
+    }
+
+    /**
+     * lowerCase first letter
+     *
+     * <pre>
+     *      StringUtils.lowerCaseFirst(null, *)     = null
+     *      StringUtils.lowerCaseFirst("", *)       = ""
+     *      StringUtils.lowerCaseFirst("ABC", *)    = "aBC"
+     * </pre>
+     *
+     * @param text
+     * @return
+     */
+    public static String lowerCaseFirst(String text) {
+        if (isBlank(text)) {
+            return text;
+        }
+        return text.substring(0, 1).toLowerCase() + text.substring(1);
+    }
+
+    /**
+     * convert underscores to hump format
+     *
+     * <pre>
+     *      StringUtils.lowerCaseFirst(null, *)             = null
+     *      StringUtils.lowerCaseFirst("", *)               = ""
+     *      StringUtils.lowerCaseFirst("aaa_bbb", *)        = "aaaBbb"
+     * </pre>
+     *
+     * @param underscoreText
+     * @return
+     */
+    public static String underlineToCamelCase(String underscoreText) {
+        if (isBlank(underscoreText)) {
+            return underscoreText;
+        }
+        StringBuilder result = new StringBuilder();
+        boolean flag = false;
+        for (int i = 0; i < underscoreText.length(); i++) {
+            char ch = underscoreText.charAt(i);
+            if ("_".charAt(0) == ch) {
+                flag = true;
+            } else {
+                if (flag) {
+                    result.append(Character.toUpperCase(ch));
+                    flag = false;
+                } else {
+                    result.append(ch);
+                }
+            }
+        }
+        return result.toString();
+    }
+
 
 }

src/test/java/com/xxl/tool/test/core/StringToolTest.java

@@ -14,4 +14,11 @@ public void test() {
         logger.info("" + StringTool.isBlank("  "));
     }
 
+    @Test
+    public void underlineToCamelCaseTest() {
+        String text = "aaa_bbb";
+        logger.info("text = " + text);
+        logger.info("result = " + StringTool.underlineToCamelCase(text));
+    }
+
 }