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The Checker Framework enhances Java's type system to make it more powerful and useful. This lets software developers detect and prevent errors in their Java programs. The Checker Framework includes compiler plug-ins ("checkers") that find bugs or verify their absence. It also permits you to write your own compiler plug-ins.
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package org.checkerframework.dataflow.analysis;

import java.util.Map;
import java.util.StringJoiner;
import javax.lang.model.type.TypeMirror;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.plumelib.util.StringsPlume;

/**
 * Implementation of a {@link TransferResult} with two non-exceptional stores. The 'then' store
 * contains information valid when the previous boolean-valued expression was true, and the 'else'
 * store contains information valid when the expression was false.
 *
 * {@link getRegularStore} returns the least upper bound of the two underlying stores.
 *
 * @param  type of the abstract value that is tracked
 * @param  the store type used in the analysis
 */
public class ConditionalTransferResult, S extends Store>
    extends TransferResult {

  /** Whether the store changed. */
  private final boolean storeChanged;

  /** The 'then' result store. */
  protected final S thenStore;

  /** The 'else' result store. */
  protected final S elseStore;

  /**
   * Create a new {@link #ConditionalTransferResult(AbstractValue, Store, Store, Map, boolean)},
   * using {@code null} for {@link #exceptionalStores}.
   *
   * 
Exceptions: If the corresponding {@link
   * org.checkerframework.dataflow.cfg.node.Node} throws an exception, then it is assumed that no
   * special handling is necessary and the store before the corresponding {@link
   * org.checkerframework.dataflow.cfg.node.Node} will be passed along any exceptional edge.
   *
   * 
Aliasing: {@code thenStore} and {@code elseStore} are not allowed to be used
   * anywhere outside of this class (including use through aliases). Complete control over the
   * objects is transferred to this class.
   *
   * @param value the abstract value produced by the transfer function
   * @param thenStore 'then' result store
   * @param elseStore 'else' result store
   * @param storeChanged whether the store changed
   * @see #ConditionalTransferResult(AbstractValue, Store, Store, Map, boolean)
   */
  public ConditionalTransferResult(
      @Nullable V value, S thenStore, S elseStore, boolean storeChanged) {
    this(value, thenStore, elseStore, null, storeChanged);
  }

  /**
   * Create a new {@link #ConditionalTransferResult(AbstractValue, Store, Store, Map, boolean)},
   * using {@code false} for whether the store changed and {@code null} for {@link
   * #exceptionalStores}.
   *
   * @param value the abstract value produced by the transfer function
   * @param thenStore {@link #thenStore}
   * @param elseStore {@link #elseStore}
   * @see #ConditionalTransferResult(AbstractValue, Store, Store, Map, boolean)
   */
  public ConditionalTransferResult(@Nullable V value, S thenStore, S elseStore) {
    this(value, thenStore, elseStore, false);
  }

  /**
   * Create a new {@link #ConditionalTransferResult(AbstractValue, Store, Store, Map, boolean)},
   * using {@code false} for the {@code storeChanged} formal parameter.
   *
   * @param value the abstract value produced by the transfer function
   * @param thenStore {@link #thenStore}
   * @param elseStore {@link #elseStore}
   * @param exceptionalStores {@link #exceptionalStores}
   * @see #ConditionalTransferResult(AbstractValue, Store, Store, Map, boolean)
   */
  public ConditionalTransferResult(
      V value, S thenStore, S elseStore, Map exceptionalStores) {
    this(value, thenStore, elseStore, exceptionalStores, false);
  }

  /**
   * Create a {@code ConditionalTransferResult} with {@code thenStore} as the resulting store if the
   * corresponding {@link org.checkerframework.dataflow.cfg.node.Node} evaluates to {@code true} and
   * {@code elseStore} otherwise.
   *
   * 
Exceptions: If the corresponding {@link
   * org.checkerframework.dataflow.cfg.node.Node} throws an exception, then the corresponding store
   * in {@code exceptionalStores} is used. If no exception is found in {@code exceptionalStores},
   * then it is assumed that no special handling is necessary and the store before the corresponding
   * {@link org.checkerframework.dataflow.cfg.node.Node} will be passed along any exceptional edge.
   *
   * Aliasing: {@code thenStore}, {@code elseStore}, and any store in {@code
   * exceptionalStores} are not allowed to be used anywhere outside of this class (including use
   * through aliases). Complete control over the objects is transferred to this class.
   *
   * @param value the abstract value produced by the transfer function
   * @param thenStore {@link #thenStore}
   * @param elseStore {@link #elseStore}
   * @param exceptionalStores {@link #exceptionalStores}
   * @param storeChanged whether the store changed; see {@link
   *     org.checkerframework.dataflow.analysis.TransferResult#storeChanged}.
   */
  public ConditionalTransferResult(
      @Nullable V value,
      S thenStore,
      S elseStore,
      @Nullable Map exceptionalStores,
      boolean storeChanged) {
    super(value, exceptionalStores);
    this.thenStore = thenStore;
    this.elseStore = elseStore;
    this.storeChanged = storeChanged;
  }

  /** The regular result store. */
  @Override
  public S getRegularStore() {
    return thenStore.leastUpperBound(elseStore);
  }

  @Override
  public S getThenStore() {
    return thenStore;
  }

  @Override
  public S getElseStore() {
    return elseStore;
  }

  @Override
  public boolean containsTwoStores() {
    return true;
  }

  @Override
  public String toString() {
    StringJoiner result = new StringJoiner(System.lineSeparator());
    result.add("RegularTransferResult(");
    result.add("  resultValue = " + StringsPlume.indentLinesExceptFirst(2, resultValue));
    result.add("  thenStore = " + StringsPlume.indentLinesExceptFirst(2, thenStore));
    result.add("  elseStore = " + StringsPlume.indentLinesExceptFirst(2, elseStore));
    result.add(")");
    return result.toString();
  }

  @Override
  public boolean storeChanged() {
    return storeChanged;
  }
}