src/main/java/com/android/tools/r8/utils/ThrowingIterator.java

// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

package com.android.tools.r8.utils;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

public abstract class ThrowingIterator<T, E extends Exception> {

  public abstract boolean hasNext();

  public abstract T next() throws E;

  public T computeNextIfAbsent(ThrowingSupplier<T, E> supplier) throws E {
    if (hasNext()) {
      return next();
    }
    return supplier.get();
  }

  public List<T> take(int number) throws E {
    List<T> result = new ArrayList<>(number);
    while (number > 0) {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      result.add(next());
      number--;
    }
    return result;
  }

  public static <T, E extends Exception> ThrowingIterator<T, E> fromIterator(Iterator<T> it) {
    return new ThrowingIterator<>() {
      @Override
      public boolean hasNext() {
        return it.hasNext();
      }

      @Override
      public T next() throws E {
        return it.next();
      }
    };
  }
}