increase the test coverage

Author: Federico2014

common/src/main/java/org/tron/common/utils/StringUtil.java

@@ -46,9 +46,16 @@ public static ByteString hexString2ByteString(String hexString) {
   }
 
   public static boolean isHexadecimal(String str) {
+    if (str == null || str.length() == 0) {
+      return false;
+    }
+    if (str.length() % 2 != 0) {
+      return false;
+    }
+
     for (int i = 0; i < str.length(); i++) {
       char c = str.charAt(i);
-      if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))) {
+      if (Character.digit(c, 16) == -1) {
         return false;
       }
     }

framework/src/test/java/org/tron/core/config/args/LocalWitnessTest.java

@@ -26,6 +26,7 @@
 import org.junit.rules.TemporaryFolder;
 import org.tron.common.utils.LocalWitnesses;
 import org.tron.common.utils.PublicMethod;
+import org.tron.common.utils.StringUtil;
 import org.tron.core.Constant;
 
 public class LocalWitnessTest {
@@ -108,7 +109,7 @@ public void testInvalidPrivateKey() {
       localWitnesses.addPrivateKeys(null);
       fail("should throw IllegalArgumentException");
     } catch (IllegalArgumentException e) {
-      Assert.assertTrue(e.getMessage().contains("private key must be"));
+      Assert.assertTrue(e.getMessage().contains("private key must be 64 hex string"));
     } catch (Exception e) {
       fail("should IllegalArgumentException，actual exception: " + e.getClass().getSimpleName());
     }
@@ -117,7 +118,7 @@ public void testInvalidPrivateKey() {
       localWitnesses.addPrivateKeys("");
       fail("should throw IllegalArgumentException");
     } catch (IllegalArgumentException e) {
-      Assert.assertTrue(e.getMessage().contains("private key must be"));
+      Assert.assertTrue(e.getMessage().contains("private key must be 64 hex string"));
     } catch (Exception e) {
       fail("should IllegalArgumentException，actual exception: " + e.getClass().getSimpleName());
     }
@@ -126,7 +127,16 @@ public void testInvalidPrivateKey() {
       localWitnesses.addPrivateKeys("  ");
       fail("should throw IllegalArgumentException");
     } catch (IllegalArgumentException e) {
-      Assert.assertTrue(e.getMessage().contains("private key must be"));
+      Assert.assertTrue(e.getMessage().contains("private key must be 64 hex string"));
+    } catch (Exception e) {
+      fail("should IllegalArgumentException，actual exception: " + e.getClass().getSimpleName());
+    }
+
+    try {
+      localWitnesses.addPrivateKeys("11111");
+      fail("should throw IllegalArgumentException");
+    } catch (IllegalArgumentException e) {
+      Assert.assertTrue(e.getMessage().contains("private key must be 64 hex string"));
     } catch (Exception e) {
       fail("should IllegalArgumentException，actual exception: " + e.getClass().getSimpleName());
     }
@@ -152,6 +162,16 @@ public void testInvalidPrivateKey() {
     }
   }
 
+  @Test
+  public void testHexStringFormat() {
+    Assert.assertTrue(StringUtil.isHexadecimal("0123456789abcdefABCDEF"));
+    Assert.assertFalse(StringUtil.isHexadecimal(null));
+    Assert.assertFalse(StringUtil.isHexadecimal(""));
+    Assert.assertFalse(StringUtil.isHexadecimal("abc"));
+    Assert.assertFalse(StringUtil.isHexadecimal(" "));
+    Assert.assertFalse(StringUtil.isHexadecimal("123xyz"));
+  }
+
   @Test
   public void getPrivateKey() {
     Assert.assertEquals(Lists