docs(sample): add custom retry algo samples

samples/snippets/src/main/java/com/example/bigquery/SetCustomRetryAlgorithm.java

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+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.bigquery;
+
+// [START bigquery_set_custom_retry_algorithm]
+import com.google.api.gax.retrying.ResultRetryAlgorithm;
+import com.google.cloud.ExceptionHandler;
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQueryOptions;
+import java.util.concurrent.TimeoutException;
+
+public class SetCustomRetryAlgorithm {
+  // In order to use a custom retry algorithm, you must implement a custom
+  // Interceptor that implements the ExceptionHandler.Interceptor interface.
+  public static final ExceptionHandler.Interceptor EXCEPTION_HANDLER_INTERCEPTOR =
+      new ExceptionHandler.Interceptor() {
+        public ExceptionHandler.Interceptor.RetryResult afterEval(
+            Exception exception, ExceptionHandler.Interceptor.RetryResult retryResult) {
+          return RetryResult.CONTINUE_EVALUATION;
+        }
+
+        public ExceptionHandler.Interceptor.RetryResult beforeEval(Exception exception) {
+          return RetryResult.CONTINUE_EVALUATION;
+        }
+      };
+
+  public static void main(String... args) {
+    // TODO(developer): Replace projectId and exception classes before running
+    //  the sample.
+    String projectId = "project-id";
+    ResultRetryAlgorithm<?> retryAlgorithm =
+        ExceptionHandler.newBuilder()
+            .abortOn(RuntimeException.class)
+            .retryOn(TimeoutException.class)
+            .addInterceptors(EXCEPTION_HANDLER_INTERCEPTOR)
+            .build();
+    setCustomRetryAlgorithm(projectId, retryAlgorithm);
+  }
+
+  public static void setCustomRetryAlgorithm(
+      String projectId, ResultRetryAlgorithm<?> retryAlgorithm) {
+    BigQueryOptions options =
+        BigQueryOptions.newBuilder()
+            .setProjectId(projectId)
+            .setResultRetryAlgorithm(retryAlgorithm)
+            .build();
+
+    BigQuery bigquery = options.getService();
+
+    System.out.println(bigquery.getOptions().getResultRetryAlgorithm());
+  }
+}
+// [END bigquery_set_custom_retry_algorithm]

samples/snippets/src/test/java/com/example/bigquery/SetCustomRetryAlgorithmIT.java

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+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.bigquery;
+
+import static com.google.common.truth.Truth.assertThat;
+import static junit.framework.TestCase.assertNotNull;
+
+import com.google.api.gax.retrying.ResultRetryAlgorithm;
+import com.google.cloud.ExceptionHandler;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.concurrent.TimeoutException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class SetCustomRetryAlgorithmIT {
+  private final Logger log = Logger.getLogger(this.getClass().getName());
+  private ByteArrayOutputStream bout;
+  private PrintStream out;
+  private PrintStream originalPrintStream;
+
+  private static final String PROJECT_ID = requireEnvVar("GOOGLE_CLOUD_PROJECT");
+
+  private static String requireEnvVar(String varName) {
+    String value = System.getenv(varName);
+    assertNotNull(
+        "Environment variable " + varName + " is required to perform these tests.",
+        System.getenv(varName));
+    return value;
+  }
+
+  @Before
+  public void setUp() throws Exception {
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    originalPrintStream = System.out;
+    System.setOut(out);
+  }
+
+  @After
+  public void tearDown() {
+    System.out.flush();
+    System.setOut(originalPrintStream);
+    log.log(Level.INFO, "\n" + bout.toString());
+  }
+
+  @Test
+  public void testSetCustomRetryAlgorithm() {
+    ResultRetryAlgorithm<?> retryAlgorithm =
+        ExceptionHandler.newBuilder()
+            .abortOn(RuntimeException.class)
+            .retryOn(TimeoutException.class)
+            .addInterceptors(SetCustomRetryAlgorithm.EXCEPTION_HANDLER_INTERCEPTOR)
+            .build();
+
+    SetCustomRetryAlgorithm.setCustomRetryAlgorithm(PROJECT_ID, retryAlgorithm);
+    assertThat(bout.toString().contains("com.google.cloud.ExceptionHandler"));
+  }
+}