Scala获得空指针异常，如何以最小的更改解决它

Question

我有以下scala代码，其中一半是机器生成的，一半是手工修改的。我收到一个空指针异常，我想我没有重写方法，它会导致错误。

代码有点大，所以我不能在此处发布整个代码，但是我将回购URL放在底部。

我知道这个问题太笼统，但是我所寻找的只是能够以最小的修改来运行代码。谢谢。

object tiny_circular_simple_implicit {
  val tiny_circular_simple_loaded = true;;
  type T_TINY_CIRCULAR_SIMPLE[T_T] = T_T;
}
import basic_implicit._;
trait C_TINY_CIRCULAR_SIMPLE[T_Result, T_T] extends C_TYPE[T_Result] with C_TINY[T_Result] {
  type T_IntegerLattice;
  val t_IntegerLattice : C_NULL[T_IntegerLattice]with C_MAX_LATTICE[T_IntegerLattice,T_Integer];
  val v_s_bag1 : (T_Wood) => T_IntegerLattice;
  val v_s_bag2 : (T_Wood) => T_IntegerLattice;
  val v_s : (T_Wood) => T_Integer;
  val v_result : (T_Root) => T_Integer;
}

class M_TINY_CIRCULAR_SIMPLE[T_T](name : String,val t_T : C_TYPE[T_T] with C_TINY[T_T])
  extends Module(name)
    with C_TINY_CIRCULAR_SIMPLE[T_T,T_T]
{
  type T_Result = T_T;
  val v_equal = t_T.v_equal;
  val v_string = t_T.v_string;
  val v_assert = t_T.v_assert;
  val v_node_equivalent = t_T.v_node_equivalent;
  type T_Root = t_T.T_Root;
  val t_Root = t_T.t_Root;
  type T_Wood = t_T.T_Wood;
  val t_Wood = t_T.t_Wood;
  val p_root = t_T.p_root;
  val v_root = t_T.v_root;
  val p_branch = t_T.p_branch;
  val v_branch = t_T.v_branch;
  val p_leaf = t_T.p_leaf;
  val v_leaf = t_T.v_leaf;

  val t_Result : this.type = this;
  val t_IntegerLattice = new M_MAX_LATTICE_Numeric[T_Integer]("IntegerLattice",t_Integer,0);
  type T_IntegerLattice = /*TI*/T_MAX_LATTICE[T_Integer];
  private class E_s_bag1(anchor : T_Wood) extends Evaluation[T_Wood,T_IntegerLattice](anchor,anchor.toString()+"."+"s_bag1") with CircularEvaluation[T_Wood,T_IntegerLattice] {
    def lattice() : C_LATTICE[T_IntegerLattice] = t_IntegerLattice;

    override def compute : ValueType = c_s_bag1(anchor);
  }
  private object a_s_bag1 extends Attribute[T_Wood,T_IntegerLattice](t_Wood,t_IntegerLattice,"s_bag1") {
    override def createEvaluation(anchor : T_Wood) : Evaluation[T_Wood,T_IntegerLattice] = new E_s_bag1(anchor);
  }
  val v_s_bag1 : T_Wood => T_IntegerLattice = a_s_bag1.get _;

  private class E_s_bag2(anchor : T_Wood) extends Evaluation[T_Wood,T_IntegerLattice](anchor,anchor.toString()+"."+"s_bag2") with CircularEvaluation[T_Wood,T_IntegerLattice] {
    def lattice() : C_LATTICE[T_IntegerLattice] = t_IntegerLattice;

    override def compute : ValueType = c_s_bag2(anchor);
  }
  private object a_s_bag2 extends Attribute[T_Wood,T_IntegerLattice](t_Wood,t_IntegerLattice,"s_bag2") {
    override def createEvaluation(anchor : T_Wood) : Evaluation[T_Wood,T_IntegerLattice] = new E_s_bag2(anchor);
  }
  val v_s_bag2 : T_Wood => T_IntegerLattice = a_s_bag2.get _;

  private class E_s(anchor : T_Wood) extends Evaluation[T_Wood,T_Integer](anchor,anchor.toString()+"."+"s") {
    override def compute : ValueType = c_s(anchor);
  }
  private object a_s extends Attribute[T_Wood,T_Integer](t_Wood,t_Integer,"s") {
    override def createEvaluation(anchor : T_Wood) : Evaluation[T_Wood,T_Integer] = new E_s(anchor);
  }
  val v_s : T_Wood => T_Integer = a_s.get _;

  private class E_result(anchor : T_Root) extends Evaluation[T_Root,T_Integer](anchor,anchor.toString()+"."+"result") {
    override def compute : ValueType = c_result(anchor);
  }
  private object a_result extends Attribute[T_Root,T_Integer](t_Root,t_Integer,"result") {
    override def createEvaluation(anchor : T_Root) : Evaluation[T_Root,T_Integer] = new E_result(anchor);
  }
  val v_result : T_Root => T_Integer = a_result.get _;

  private class E1_i(anchor : t_Result.T_Wood) extends Evaluation[t_Result.T_Wood,T_IntegerLattice](anchor,anchor.toString()+"."+"i") with CircularEvaluation[t_Result.T_Wood,T_IntegerLattice] {
    def lattice() : C_LATTICE[T_IntegerLattice] = t_IntegerLattice;

    override def compute : ValueType = c1_i(anchor);
  }
  private object a1_i extends Attribute[t_Result.T_Wood,T_IntegerLattice](t_Result.t_Wood,t_IntegerLattice,"i") {
    override def createEvaluation(anchor : t_Result.T_Wood) : Evaluation[t_Result.T_Wood,T_IntegerLattice] = new E1_i(anchor);
  }
  private class E2_i(anchor : t_Result.T_Root) extends Evaluation[t_Result.T_Root,T_IntegerLattice](anchor,anchor.toString()+"."+"i") with CircularEvaluation[t_Result.T_Root,T_IntegerLattice] {
    def lattice() : C_LATTICE[T_IntegerLattice] = t_IntegerLattice;

    override def compute : ValueType = c2_i(anchor);
  }
  private object a2_i extends Attribute[t_Result.T_Root,T_IntegerLattice](t_Result.t_Root,t_IntegerLattice,"i") {
    override def createEvaluation(anchor : t_Result.T_Root) : Evaluation[t_Result.T_Root,T_IntegerLattice] = new E2_i(anchor);
  }
  def visit_0_1(node : T_Root) : Unit = node match {
    case p_root(_,_) => visit_0_1_0(node);
  };
  def visit_0_1_0(anchor : T_Root) : Unit = anchor match {
    case p_root(v_p,v_b) => {
      // p.G[Root]'shared_info is ready now.
      // shared info for b is ready.
      visit_1_1(v_b);
      // b.s_bag1 is ready now.
      a2_i.assign(anchor,a_s_bag1.get(v_b));
      a_s_bag2.assign(v_b,new M__basic_13[ T_IntegerLattice](t_IntegerLattice).v_max(a2_i.get(anchor),5));
      visit_1_2(v_b);
      // b.s is ready now.
      a_result.assign(v_p,a_s.get(v_b));
    }
  }


  def visit_1_1(node : T_Wood) : Unit = node match {
    case p_leaf(_,_) => visit_1_1_1(node);
    case p_branch(_,_,_) => visit_1_1_0(node);
  };
  def visit_1_2(node : T_Wood) : Unit = node match {
    case p_leaf(_,_) => visit_1_2_1(node);
    case p_branch(_,_,_) => visit_1_2_0(node);
  };
  def visit_1_1_1(anchor : T_Wood) : Unit = anchor match {
    case p_leaf(v_l,v_x) => {
      // l.G[Wood]'shared_info is ready now.
      a_s_bag1.assign(v_l,v_x);
    }
  }

  def visit_1_2_1(anchor : T_Wood) : Unit = anchor match {
    case p_leaf(v_l,v_x) => {
      // l.s_bag2 is ready now.
      a_s.assign(v_l,a_s_bag2.get(v_l));
    }
  }

  def visit_1_1_0(anchor : T_Wood) : Unit = anchor match {
    case p_branch(v_b,v_x,v_y) => {
      // b.G[Wood]'shared_info is ready now.
      // shared info for x is ready.
      visit_1_1(v_x);
      // x.s_bag1 is ready now.
      // shared info for y is ready.
      visit_1_1(v_y);
      // y.s_bag1 is ready now.
      a_s_bag1.assign(v_b,new M__basic_4[ T_IntegerLattice](t_IntegerLattice).v__op_s(a_s_bag1.get(v_x),a_s_bag1.get(v_y)));
    }
  }

  def visit_1_2_0(anchor : T_Wood) : Unit = anchor match {
    case p_branch(v_b,v_x,v_y) => {
      // b.s_bag2 is ready now.
      a1_i.assign(anchor,a_s_bag2.get(v_b));
      a_s_bag2.assign(v_x,a1_i.get(anchor));
      visit_1_2(v_x);
      // x.s is ready now.
      a_s_bag2.assign(v_y,a1_i.get(anchor));
      visit_1_2(v_y);
      // y.s is ready now.
      a_s.assign(v_b,new M__basic_4[ T_Integer](t_Integer).v__op_s(a_s.get(v_x),a_s.get(v_y)));
    }
  }


  def visit() : Unit = {
    val roots = t_Root.nodes;
    // shared info for TINY_CIRCULAR_SIMPLE is ready.
    for (root <- roots) {
      visit_0_1(root);
    }
    // TINY_CIRCULAR_SIMPLE.result is ready now.
  }


  def c1_i(anchor : Any) : T_IntegerLattice = {
    anchor match {
      case p_branch(v_b,v_x,v_y) => {
        return v_s_bag2(v_b);
      }
    }
  }
  def c2_i(anchor : Any) : T_IntegerLattice = {
    anchor match {
      case p_root(v_p,v_b) => {
        return v_s_bag1(v_b);
      }
    }
  }
  def c_s_bag1(anode : T_Wood) : T_IntegerLattice = {
    val anchor = anode;
    anchor match {
      case p_leaf(v_l,v_x) => {
        if (anode eq v_l) return v_x;
      }
      case _ => {}
    }
    anchor match {
      case p_branch(v_b,v_x,v_y) => {
        if (anode eq v_b) return new M__basic_4[ T_IntegerLattice](t_IntegerLattice).v__op_s(v_s_bag1(v_x),v_s_bag1(v_y));
      }
      case _ => {}
    }
    throw Evaluation.UndefinedAttributeException(anode.toString()+".s_bag1");
  }
  def c_s_bag2(anode : T_Wood) : T_IntegerLattice = {
    val anchor = anode.parent;
    if (!(anchor eq null)) {
      val anchorNodes = anchor.myType.nodes;
      if (anchorNodes == t_Result.t_Wood.nodes) anchor match {
        case p_branch(v_b,v_x,v_y) => {
          if (anode eq v_x) return a1_i.get(anchor);
          if (anode eq v_y) return a1_i.get(anchor);
        }
        case _ => {}
      }
      if (anchorNodes == t_Result.t_Root.nodes) anchor match {
        case p_root(v_p,v_b) => {
          if (anode eq v_b) return new M__basic_13[ T_IntegerLattice](t_IntegerLattice).v_max(a2_i.get(anchor),5);
        }
        case _ => {}
      }
    }
    throw Evaluation.UndefinedAttributeException(anode.toString()+".s_bag2");
  }
  def c_s(anode : T_Wood) : T_Integer = {
    val anchor = anode;
    anchor match {
      case p_leaf(v_l,v_x) => {
        if (anode eq v_l) return v_s_bag2(v_l);
      }
      case _ => {}
    }
    anchor match {
      case p_branch(v_b,v_x,v_y) => {
        if (anode eq v_b) return new M__basic_4[ T_Integer](t_Integer).v__op_s(v_s(v_x),v_s(v_y));
      }
      case _ => {}
    }
    throw Evaluation.UndefinedAttributeException(anode.toString()+".s");
  }

  def c_result(anode : T_Root) : T_Integer = {
    val anchor = anode;
    anchor match {
      case p_root(v_p,v_b) => {
        if (anode eq v_p) return v_s(v_b);
      }
      case _ => {}
    }
    throw Evaluation.UndefinedAttributeException(anode.toString()+".result");
  }

  override def finish() : Unit = {
    visit();
    t_IntegerLattice.finish();
    super.finish();
  }

}

错误：

Type Tiny is now finished.
leaf(3)@0.s_bag1:=3
Exception in thread "main" java.lang.NullPointerException
    at CircularEvaluation.check(aps-impl.scala:486)
    at CircularEvaluation.set(aps-impl.scala:494)
    at CircularEvaluation.set$(aps-impl.scala:493)
    at M_TINY_CIRCULAR_SIMPLE$E_s_bag1.set(tiny-circular-simple.scala:39)
    at Attribute.set(aps-impl.scala:325)
    at Attribute.assign(aps-impl.scala:292)
    at M_TINY_CIRCULAR_SIMPLE.visit_1_1_1(tiny-circular-simple.scala:120)
    at M_TINY_CIRCULAR_SIMPLE.visit_1_1(tiny-circular-simple.scala:110)
    at M_TINY_CIRCULAR_SIMPLE.visit_1_1_0(tiny-circular-simple.scala:135)
    at M_TINY_CIRCULAR_SIMPLE.visit_1_1(tiny-circular-simple.scala:111)
    at M_TINY_CIRCULAR_SIMPLE.visit_0_1_0(tiny-circular-simple.scala:98)
    at M_TINY_CIRCULAR_SIMPLE.visit_0_1(tiny-circular-simple.scala:92)
    at M_TINY_CIRCULAR_SIMPLE.$anonfun$visit$1(tiny-circular-simple.scala:163)
    at M_TINY_CIRCULAR_SIMPLE.$anonfun$visit$1$adapted(tiny-circular-simple.scala:162)
    at scala.collection.mutable.ResizableArray.foreach(ResizableArray.scala:59)
    at scala.collection.mutable.ResizableArray.foreach$(ResizableArray.scala:52)
    at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
    at M_TINY_CIRCULAR_SIMPLE.visit(tiny-circular-simple.scala:162)
    at M_TINY_CIRCULAR_SIMPLE.finish(tiny-circular-simple.scala:248)
    at TinyCircularDriver$.delayedEndpoint$TinyCircularDriver$1(tiny-circular-driver.scala:17)
    at TinyCircularDriver$delayedInit$body.apply(tiny-circular-driver.scala:1)
    at scala.Function0.apply$mcV$sp(Function0.scala:34)
    at scala.Function0.apply$mcV$sp$(Function0.scala:34)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App.$anonfun$main$1$adapted(App.scala:76)
    at scala.collection.immutable.List.foreach(List.scala:378)
    at scala.App.main(App.scala:76)
    at scala.App.main$(App.scala:74)
    at TinyCircularDriver$.main(tiny-circular-driver.scala:1)
    at TinyCircularDriver.main(tiny-circular-driver.scala)

退出代码为1的处理完成

Repo url

Answer 1

错误发生在问题中未显示的方法中，因此无法确定实际问题是什么。但是，代码明确使用null值，这是一个非常糟糕的主意。

而不是与null进行比较，而使T_Wood键入Option，并使用适当的方法来处理不存在该值的情况。

而且，从方法中抛出异常也是一个坏主意。从这些方法返回Try并在调用方中显式处理错误。使用for作为链接返回Try的多个动作的干净方法。