src/java.base/share/classes/jdk/internal/module/ModuleHashes.java

rev 16336 : 8171373: Reduce copying during initialization of ModuleHashes
Reviewed-by: alanb, mchung, chegar

*** 147,178 ****
       * This is used by jdk.internal.module.SystemModules class
       * generated at link time.
       */
      public static class Builder {
          final String algorithm;
!         Map<String, byte[]> nameToHash;
  
!         Builder(String algorithm) {
              this.algorithm =  Objects.requireNonNull(algorithm);
          }
  
          /**
           * Sets the module hash for the given module name
           */
          public Builder hashForModule(String mn, byte[] hash) {
-             if (nameToHash == null)
-                 nameToHash = new HashMap<>();
- 
              nameToHash.put(mn, hash);
              return this;
          }
  
          /**
           * Builds a {@code ModuleHashes}.
           */
          public ModuleHashes build() {
!             if (nameToHash != null) {
                  return new ModuleHashes(algorithm, nameToHash);
              } else {
                  return null;
              }
          }
--- 147,176 ----
       * This is used by jdk.internal.module.SystemModules class
       * generated at link time.
       */
      public static class Builder {
          final String algorithm;
!         final Map<String, byte[]> nameToHash;
  
!         Builder(String algorithm, int initialCapacity) {
!             this.nameToHash = new HashMap<>(initialCapacity);
              this.algorithm =  Objects.requireNonNull(algorithm);
          }
  
          /**
           * Sets the module hash for the given module name
           */
          public Builder hashForModule(String mn, byte[] hash) {
              nameToHash.put(mn, hash);
              return this;
          }
  
          /**
           * Builds a {@code ModuleHashes}.
           */
          public ModuleHashes build() {
!             if (!nameToHash.isEmpty()) {
                  return new ModuleHashes(algorithm, nameToHash);
              } else {
                  return null;
              }
          }