Fix toString in ConnectionPolicy (Azure#44961)

* fix toString in ConnectionPolicy

* use Objects.toString

Author: nehrao1

sdk/cosmos/azure-cosmos-tests/src/test/java/com/azure/cosmos/ConnectionPolicyTest.java

@@ -48,11 +48,13 @@ public void usingMultipleWriteRegions() {
     public void connectionPolicyDirectConnectionToString() {
         ConnectionPolicy policy = new ConnectionPolicy(DirectConnectionConfig.getDefaultConfig());
         assertThat(policy.toString()).isNotEmpty();
+        assertThat(policy.toString()).isNotEqualTo("null");
     }
 
     @Test(groups = { "unit" })
     public void connectionPolicyGatewayConnectionToString() {
         ConnectionPolicy policy = new ConnectionPolicy(GatewayConnectionConfig.getDefaultConfig());
         assertThat(policy.toString()).isNotEmpty();
+        assertThat(policy.toString()).isNotEqualTo("null");
     }
 }

sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/ConnectionPolicy.java

@@ -14,6 +14,7 @@
 import java.time.Duration;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 import java.util.function.Supplier;
 
 /**
@@ -669,7 +670,7 @@ public String toString() {
             ", minConnectionPoolSizePerEndpoint=" + minConnectionPoolSizePerEndpoint +
             ", openConnectionsConcurrency=" + openConnectionsConcurrency +
             ", aggressiveWarmupConcurrency=" + aggressiveWarmupConcurrency +
-            ", pendingAcquireMaxCount=" + this.pendingAcquireMaxCount != null ? String.valueOf(this.pendingAcquireMaxCount) : "DEFAULT" +
+            ", pendingAcquireMaxCount=" + Objects.toString(this.pendingAcquireMaxCount,"DEFAULT") +
             '}';
     }
 }