small improvement (min,max)

core/src/main/java/io/github/mmm/scanner/AbstractCharStreamScanner.java

@@ -1417,11 +1417,14 @@ public boolean skipOver(String substring, boolean ignoreCase, CharFilter stopFil
   }
 
   @Override
-  public String readWhile(CharFilter filter, int max) {
+  public String readWhile(CharFilter filter, int min, int max) {
 
     if (max < 0) {
       throw new IllegalArgumentException("Max must NOT be negative: " + max);
     }
+    if (max < min) {
+      throw new IllegalArgumentException("Min (" + min + ") must be less or requal to max (" + max + ")");
+    }
     StringBuilder builder = null;
     if (this.offset >= this.limit) {
       fill();
@@ -1439,7 +1442,7 @@ public String readWhile(CharFilter filter, int max) {
       while (this.offset < end) {
         char c = this.buffer[this.offset];
         if (!filter.accept(c)) {
-          return getAppended(builder, start, this.offset);
+          return requireMin(getAppended(builder, start, this.offset), min, filter);
         }
         handleChar(c);
         this.offset++;
@@ -1448,11 +1451,30 @@ public String readWhile(CharFilter filter, int max) {
       remain -= len;
       builder = append(builder, start, this.offset);
       if ((remain == 0) || !fill()) {
-        return eot(builder, true);
+        return requireMin(eot(builder, true), min, filter);
       }
     }
   }
 
+  /**
+   * @param actual the actual number of characters.
+   * @param min the minimum number of characters required.
+   * @param filter the {@link CharFilter} that was used.
+   */
+  protected void requireMin(int actual, int min, CharFilter filter) {
+
+    if (actual < min) {
+      throw new IllegalStateException(
+          "Required at least " + min + " character(s) (" + filter.getDescription() + ") but found only " + actual);
+    }
+  }
+
+  private String requireMin(String result, int min, CharFilter filter) {
+
+    requireMin(result.length(), min, filter);
+    return result;
+  }
+
   /**
    * @return the {@link String} with the characters that have already been parsed but are still available in the
    *         underlying buffer. May be used for debugging or error messages.

core/src/main/java/io/github/mmm/scanner/CharSequenceScanner.java

@@ -470,7 +470,7 @@ public void require(String expected, boolean ignoreCase) {
   }
 
   @Override
-  public String readWhile(CharFilter filter, int max) {
+  public String readWhile(CharFilter filter, int min, int max) {
 
     int currentPos = this.offset;
     int len = skipWhile(filter, max);

core/src/main/java/io/github/mmm/scanner/CharStreamScanner.java

@@ -305,17 +305,20 @@ default String readUntil(CharFilter filter, boolean acceptEnd, String stop, bool
   /**
    * @param stopFilter the {@link CharFilter} that decides which characters to {@link CharFilter#accept(char) accept} as
    *        stop characters.
-   * @param maxLength the (maximum) length of the characters to consume.
+   * @param min the minimum number of characters expected.
+   * @param max the (maximum) length of the characters to consume.
    * @return the {@link String} with all consumed characters excluding the stop character. If no {@code stop} character
    *         was found until {@code maxLength} characters have been consumed, this method behaves like {@link #read(int)
    *         read(maxLength)}.
+   * @throws IllegalStateException if less than the minimum number of characters have been
+   *         {@link CharFilter#accept(char) rejected}.
    * @see #read(int)
-   * @see #readWhile(CharFilter, int)
+   * @see #readWhile(CharFilter, int, int)
    * @see #peekUntil(CharFilter, int)
    */
-  default String readUntil(CharFilter stopFilter, int maxLength) {
+  default String readUntil(CharFilter stopFilter, int min, int max) {
 
-    return readWhile(stopFilter.negate(), maxLength);
+    return readWhile(stopFilter.negate(), min, max);
   }
 
   /**
@@ -326,13 +329,13 @@ default String readUntil(CharFilter stopFilter, int maxLength) {
    *
    * @see #skipWhile(CharFilter)
    *
-   * @param filter is used to {@link CharFilter#accept(char) decide} which characters should be accepted.
+   * @param filter used to {@link CharFilter#accept(char) decide} which characters should be accepted.
    * @return a string with all characters {@link CharFilter#accept(char) accepted} by the given {@code filter}. Will be
    *         the empty string if no character was accepted.
    */
   default String readWhile(CharFilter filter) {
 
-    return readWhile(filter, Integer.MAX_VALUE);
+    return readWhile(filter, 0, Integer.MAX_VALUE);
   }
 
   /**
@@ -345,13 +348,16 @@ default String readWhile(CharFilter filter) {
    *
    * @see #skipWhile(char)
    *
-   * @param filter is used to {@link CharFilter#accept(char) decide} which characters should be accepted.
-   * @param max is the maximum number of characters that should be read.
+   * @param filter used to {@link CharFilter#accept(char) decide} which characters should be accepted.
+   * @param min the minimum number of characters expected.
+   * @param max the maximum number of characters that should be read.
    * @return a string with all characters {@link CharFilter#accept(char) accepted} by the given {@code filter} limited
    *         to the length of {@code max} and the {@link #hasNext() end} of this scanner. Will be the empty string if no
    *         character was accepted.
+   * @throws IllegalStateException if less than the minimum number of characters have been
+   *         {@link CharFilter#accept(char) accepted}.
    */
-  String readWhile(CharFilter filter, int max);
+  String readWhile(CharFilter filter, int min, int max);
 
   /**
    * @return a {@link String} with the data until the end of the current line or the end of the data. Will be

core/src/test/java/io/github/mmm/scanner/AbstractCharStreamScannerTest.java

@@ -712,12 +712,12 @@ public void testReadWhile() {
     // then
     assertThat(scanner.readWhile(textFilter)).isEqualTo("abc");
     assertThat(scanner.readWhile(textFilter)).isEmpty();
-    assertThat(scanner.readWhile(textFilter, 0)).isEmpty();
+    assertThat(scanner.readWhile(textFilter, 0, 0)).isEmpty();
     assertThat(scanner.readWhile(spaceFilter)).isEqualTo(" ");
     assertThat(scanner.readWhile(textFilter)).isEqualTo("def");
     assertThat(scanner.readWhile(spaceFilter)).isEqualTo("  ");
-    assertThat(scanner.readWhile(textFilter, 2)).isEqualTo("gh");
-    assertThat(scanner.readWhile(textFilter, 2)).isEqualTo("i");
+    assertThat(scanner.readWhile(textFilter, 0, 2)).isEqualTo("gh");
+    assertThat(scanner.readWhile(textFilter, 0, 2)).isEqualTo("i");
     assertThat(scanner.hasNext()).isFalse();
     assertThat(scanner.getPosition()).isEqualTo(12);
     assertThat(scanner.getColumn()).isEqualTo(13);