Add example for each function

Author: sakthivelmanii

google-cloud-spanner/src/main/java/com/google/cloud/spanner/StructReader.java

@@ -179,6 +179,13 @@ default float getFloat(String columnName) {
   /**
    * @param columnIndex index of the column
    * @return the value of a column with type T. return value(T) can be null.
+   * <p>
+   * Example:
+   * <p>
+   * Struct row = ...
+   * String name = row.getOrNull(1, row::getString)
+   * </p>
+   * </p>
    */
   default <T> T getOrNull(int columnIndex, Function<Integer, T> function) {
     return isNull(columnIndex) ? null : function.apply(columnIndex);
@@ -187,6 +194,13 @@ default <T> T getOrNull(int columnIndex, Function<Integer, T> function) {
   /**
    * @param columnName index of the column
    * @return the value of a column with type T. return value(T) can be null.
+   * <p>
+   * Example:
+   * <p>
+   * Struct row = ...
+   * String name = row.getOrNull("name", row::getString)
+   * </p>
+   * </p>
    */
   default <T> T getOrNull(String columnName, Function<String, T> function) {
     return isNull(columnName) ? null : function.apply(columnName);
@@ -195,6 +209,13 @@ default <T> T getOrNull(String columnName, Function<String, T> function) {
   /**
    * @param columnIndex index of the column
    * @return the value of a column with type T. if column value is null, returns default value.
+   * <p>
+   * Example:
+   * <p>
+   * Struct row = ...
+   * String name = row.getOrDefault(1, row::getString, "")
+   * </p>
+   * </p>
    */
   default <T> T getOrDefault(int columnIndex, Function<Integer, T> function, T defaultValue) {
     return isNull(columnIndex) ? defaultValue : function.apply(columnIndex);
@@ -203,6 +224,13 @@ default <T> T getOrDefault(int columnIndex, Function<Integer, T> function, T def
   /**
    * @param columnName name of the column
    * @return the value of a column with type T. if column value is null, returns default value.
+   * <p>
+   * Example:
+   * <p>
+   * Struct row = ...
+   * String name = row.getOrDefault("name", row::getString, "")
+   * </p>
+   * </p>
    */
   default <T> T getOrDefault(String columnName, Function<String, T> function, T defaultValue) {
     return isNull(columnName) ? defaultValue : function.apply(columnName);

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITReadOnlyTxnTest.java

@@ -21,6 +21,7 @@
 import static org.junit.Assert.fail;
 
 import com.google.cloud.Timestamp;
+import com.google.cloud.spanner.AbstractStructReader;
 import com.google.cloud.spanner.Database;
 import com.google.cloud.spanner.DatabaseClient;
 import com.google.cloud.spanner.IntegrationTestEnv;
@@ -32,14 +33,17 @@
 import com.google.cloud.spanner.ResultSet;
 import com.google.cloud.spanner.Statement;
 import com.google.cloud.spanner.Struct;
+import com.google.cloud.spanner.StructReader;
 import com.google.cloud.spanner.TimestampBound;
 import com.google.common.collect.ImmutableList;
 import java.util.Collections;
 import java.util.List;
 import java.util.NavigableMap;
 import java.util.TreeMap;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
 import javax.annotation.Nullable;
+import org.apache.commons.math3.analysis.function.Abs;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.ClassRule;
@@ -133,6 +137,10 @@ public void singleStrong() {
     ReadOnlyTransaction readContext = client.singleUseReadOnlyTransaction();
     Struct row = readRow(readContext);
     assertThat(row).isNotNull();
+    row.getString("StringValue");
+    String name = getOrNull(row, 0, row::getString);
+    // String name = row.getOrNull(0, row::getString);
+    assertThat(name).isEqualTo(expected.value);
     assertThat(row.getString(0)).isEqualTo(expected.value);
     assertThat(readContext.getReadTimestamp()).isAtLeast(expected.timestamp);
 
@@ -141,6 +149,10 @@ public void singleStrong() {
     assertThat(row.getString(0)).isEqualTo(expected.value);
   }
 
+  <T> T getOrNull(Struct row, int columnIndex, Function<Integer, T> function) {
+    return row.isNull(columnIndex) ? null : function.apply(columnIndex);
+  }
+
   @Test
   public void singleReadTimestamp() {
     History expected = history.get(2);