Deprecate trace-propagators StringUtils to make package private. (#2481)

* Make trace-propagators StringUtils package private.

* Deprecate

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/B3PropagatorExtractorMultipleHeaders.java

@@ -14,6 +14,7 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.Immutable;
 
 @Immutable
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 final class B3PropagatorExtractorMultipleHeaders implements B3PropagatorExtractor {
   private static final Logger logger =
       Logger.getLogger(B3PropagatorExtractorMultipleHeaders.class.getName());

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/B3PropagatorExtractorSingleHeader.java

@@ -14,6 +14,7 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.Immutable;
 
 @Immutable
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 final class B3PropagatorExtractorSingleHeader implements B3PropagatorExtractor {
   private static final Logger logger =
       Logger.getLogger(B3PropagatorExtractorSingleHeader.class.getName());

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/Common.java

@@ -19,6 +19,7 @@ import javax.annotation.concurrent.Immutable;
  * B3Propagator.
  */
 @Immutable
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 final class Common {
   private static final Logger logger = Logger.getLogger(Common.class.getName());
 

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/JaegerPropagator.java

@@ -31,6 +31,7 @@ import javax.annotation.concurrent.Immutable;
  * Format</a>.
  */
 @Immutable
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 public final class JaegerPropagator implements TextMapPropagator {
 
   private static final Logger logger = Logger.getLogger(JaegerPropagator.class.getName());

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/OtTracerPropagator.java

@@ -26,6 +26,7 @@ import javax.annotation.concurrent.Immutable;
  * TextMapPropagator</a>.
  */
 @Immutable
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 public final class OtTracerPropagator implements TextMapPropagator {
 
   static final String TRACE_ID_HEADER = "ot-tracer-traceid";

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/StringUtils.java

@@ -14,7 +14,13 @@ package io.opentelemetry.extension.trace.propagation;
 import java.util.Objects;
 import javax.annotation.concurrent.Immutable;
 
+/**
+ * Utilities for working with strings.
+ *
+ * @deprecated Will be removed without a replacement
+ */
 @Immutable
+@Deprecated
 public final class StringUtils {
 
   /**
@@ -37,7 +43,9 @@ public final class StringUtils {
    * @param padChar the character to insert at the beginning of the result until the minimum length
    *     is reached
    * @return the padded string
+   * @deprecated Will be removed without a replacement
    */
+  @Deprecated
   public static String padStart(String string, int minLength, char padChar) {
     Objects.requireNonNull(string);
     if (string.length() >= minLength) {
@@ -59,7 +67,9 @@ public final class StringUtils {
    *
    * @param string a string reference to check
    * @return {@code true} if the string is null or is the empty string
+   * @deprecated Will be removed without a replacement
    */
+  @Deprecated
   public static boolean isNullOrEmpty(String string) {
     return string == null || string.isEmpty();
   }
@@ -71,7 +81,9 @@ public final class StringUtils {
    * @param minLength the minimum length the resulting padded string must have. Can be zero or
    *     negative, in which case the input string is always returned.
    * @return the padded string
+   * @deprecated Will be removed without a replacement
    */
+  @Deprecated
   public static String padLeft(String value, int minLength) {
     return padStart(value, minLength, '0');
   }

extensions/trace-propagators/src/test/java/io/opentelemetry/extension/trace/propagation/B3PropagatorTest.java

@@ -26,6 +26,7 @@ import javax.annotation.Nullable;
 import org.junit.jupiter.api.Test;
 
 /** Unit tests for {@link B3Propagator}. */
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 class B3PropagatorTest {
 
   private static final TraceState TRACE_STATE_DEFAULT = TraceState.builder().build();

extensions/trace-propagators/src/test/java/io/opentelemetry/extension/trace/propagation/StringUtilsTest.java

@@ -10,6 +10,7 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import org.junit.jupiter.api.Test;
 
+@SuppressWarnings("deprecation") // Remove after StringUtils is made package-private
 class StringUtilsTest {
 
   @Test