fixed StringCharBuffer (#498)

src/classes/modules/java.base/java/nio/ByteBuffer.java

@@ -263,6 +263,9 @@ public ByteBuffer putLong(long x) {
 
     return this;
   }
+  public int arrayOffset(){
+    return offset;
+  }
 
   @Override
   public byte[] array() {
@@ -316,4 +319,9 @@ public boolean equals(Object ob) {
   Object base() {
     return array;
   }
+  @Override
+  public final ByteBuffer flip() {
+    super.flip();
+    return this;
+  }
 }

src/classes/modules/java.base/java/nio/CharBuffer.java

@@ -88,6 +88,9 @@ public static CharBuffer wrap(CharSequence outMess) {
     charBuffer.flip();
     return charBuffer;
   }
+  public int arrayOffset(){
+    return offset;
+  }
 
   @Override
   public char[] array() {

src/tests/CharBufferTest.java

@@ -0,0 +1,16 @@
+import gov.nasa.jpf.util.test.TestJPF;
+import org.junit.Test;
+
+import java.nio.CharBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.StandardCharsets;
+
+public class CharBufferTest extends TestJPF {
+    @Test
+    public void Test_Wrap() throws CharacterCodingException {
+        if(verifyNoPropertyViolation()){
+            java.nio.charset.StandardCharsets.UTF_8.newEncoder().encode(java.nio.CharBuffer.wrap("heyo"));
+        }
+    }
+}