fix: apply AI bot suggestion for year 2262 overflow

Change-Id: Iade245d7881798735bfb10598d9d1b4b4db0f4a1

Author: kanchi12P

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/models/Mutation.java

@@ -34,7 +34,6 @@
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 import java.time.Instant;
-import java.time.temporal.ChronoUnit;
 import java.util.List;
 import javax.annotation.Nonnull;
 
@@ -157,7 +156,8 @@ public Mutation setCell(
   @Override
   public Mutation setCell(
       @Nonnull String familyName, @Nonnull ByteString qualifier, @Nonnull ByteString value) {
-    long timestamp = Instant.EPOCH.until(Instant.now(), ChronoUnit.MICROS);
+    Instant now = Instant.now();
+    long timestamp = now.getEpochSecond() * 1_000_000L + now.getNano() / 1_000;
 
     return setCell(familyName, qualifier, timestamp, value, TimestampOrigin.CLIENT_AUTO_GENERATED);
   }
@@ -176,7 +176,7 @@ private Mutation setCell(
       @Nonnull ByteString qualifier,
       long timestamp,
       @Nonnull ByteString value,
-      TimestampOrigin timestampOrigin) {
+      @Nonnull TimestampOrigin timestampOrigin) {
     Validations.validateFamily(familyName);
     Preconditions.checkNotNull(qualifier, "qualifier can't be null.");
     Preconditions.checkNotNull(value, "value can't be null.");

java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/models/MutationTest.java

@@ -32,7 +32,6 @@
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.time.Instant;
-import java.time.temporal.ChronoUnit;
 import java.util.List;
 import org.junit.Before;
 import org.junit.Test;
@@ -51,7 +50,8 @@ public void setUp() {
 
   @Test
   public void setCellTest() {
-    long minTimestamp = Instant.EPOCH.until(Instant.now(), ChronoUnit.MICROS);
+    Instant minInstant = Instant.now();
+    long minTimestamp = minInstant.getEpochSecond() * 1_000_000L + minInstant.getNano() / 1_000;
 
     mutation
         .setCell(
@@ -68,7 +68,8 @@ public void setCellTest() {
 
     List<com.google.bigtable.v2.Mutation> actual = mutation.getMutations();
 
-    long maxTimestamp = Instant.EPOCH.until(Instant.now(), ChronoUnit.MICROS);
+    Instant maxInstant = Instant.now();
+    long maxTimestamp = maxInstant.getEpochSecond() * 1_000_000L + maxInstant.getNano() / 1_000;
     com.google.common.collect.Range<Long> expectedTimestampRange =
         com.google.common.collect.Range.closed(minTimestamp, maxTimestamp);