fix: replace instanceof assertions with typed catch to satisfy SpotBugs JUA

SpotBugs JUA flags Assert.assertTrue(e instanceof T) because the message
hides what type was actually thrown on failure.  Using a typed catch block
is stricter: any unexpected exception type propagates as a test error with
the full stack trace, which is more informative than a failed boolean
assertion.

Author: allanrogerr

api/src/test/java/io/minio/RetryTest.java

@@ -388,11 +388,9 @@ public void testNoRetryOn404() throws Exception {
       try {
         client.listBuckets();
         Assert.fail("expected exception");
-      } catch (Exception e) {
-        Assert.assertTrue("expected ErrorResponseException", e instanceof ErrorResponseException);
-        ErrorResponseException ere = (ErrorResponseException) e;
-        Assert.assertEquals("NoSuchBucket", ere.errorResponse().code());
-        Assert.assertEquals(404, ere.response().code());
+      } catch (ErrorResponseException e) {
+        Assert.assertEquals("NoSuchBucket", e.errorResponse().code());
+        Assert.assertEquals(404, e.response().code());
       }
       // Must not retry — only 1 request should have been made
       Assert.assertEquals(1, server.getRequestCount());
@@ -419,11 +417,9 @@ public void testNoRetryOn403() throws Exception {
       try {
         client.listBuckets();
         Assert.fail("expected exception");
-      } catch (Exception e) {
-        Assert.assertTrue("expected ErrorResponseException", e instanceof ErrorResponseException);
-        ErrorResponseException ere = (ErrorResponseException) e;
-        Assert.assertEquals("AccessDenied", ere.errorResponse().code());
-        Assert.assertEquals(403, ere.response().code());
+      } catch (ErrorResponseException e) {
+        Assert.assertEquals("AccessDenied", e.errorResponse().code());
+        Assert.assertEquals(403, e.response().code());
       }
       Assert.assertEquals(1, server.getRequestCount());
     }
@@ -443,10 +439,8 @@ public void testRetryExhaustedThrowsLastError() throws Exception {
       try {
         client.listBuckets();
         Assert.fail("expected exception after exhausted retries");
-      } catch (Exception e) {
-        Assert.assertTrue(
-            "expected InvalidResponseException", e instanceof InvalidResponseException);
-        Assert.assertEquals(500, ((InvalidResponseException) e).responseCode());
+      } catch (InvalidResponseException e) {
+        Assert.assertEquals(500, e.responseCode());
       }
       Assert.assertEquals(3, server.getRequestCount());
     }