import com.google.errorprone.annotations.concurrent.LazyInit; //导入依赖的package包/类
@Override
public Description matchSynchronized(SynchronizedTree tree, VisitorState state) {
  Symbol symbol = ASTHelpers.getSymbol(stripParentheses(tree.getExpression()));
  if (!(symbol instanceof VarSymbol)) {
    return NO_MATCH;
  }

  // TODO(cushon): check that the receiver doesn't contain mutable state.
  // Currently 'this.locks[i].mu' is accepted if 'mu' is final but 'locks' is non-final.
  VarSymbol varSymbol = (VarSymbol) symbol;
  if (varSymbol.isLocal() || varSymbol.isStatic() || (varSymbol.flags() & Flags.FINAL) != 0) {
    return NO_MATCH;
  }
  if (ASTHelpers.hasAnnotation(varSymbol, LazyInit.class, state)) {
    return NO_MATCH;
  }

  Name ownerName = varSymbol.owner.enclClass().getQualifiedName();
  if (Stream.of("java.io.Writer", "java.io.Reader").anyMatch(ownerName::contentEquals)) {
    // These classes contain a non-final 'lock' variable available to subclasses, and we can't
    // make these locks final.
    return NO_MATCH;
  }

  return describeMatch(tree.getExpression());
}