java - 如何用基元替换 Integer 对象

Question

我正在制作一个数据结构，我可以:

• 添加起始位置和结束位置对
• 可以获得配对测试列表
• 有间隙的间隔

例如加(0,2),(0,1),(3,4),(6,8) 它将返回 (0,4),(6,8) 检查(2,4) - 真 check(3,8) - false，因为 4 和 6 之间有间隙。

如何修改下面的代码，例如set list和list data将包含原始int而不是对象Integer ？

编辑:我知道java泛型不能是基元，所以List是不可能的。我的动力来自于其他数据结构的实现。
例如 HashMap< Integer, Object> 基本上与 android SparseArray 相同，不同之处在于 SparseArray 使用 int 而不是 Integers 作为键。

public class GapAwareList {
  Set<Integer> list = new HashSet<>();

  public void put(int start, int end) {
    for (int i = start; i <= end; i++) {
      list.add(i);
    }
  }

  public void remove(int start, int end) {
    for (int i = start; i <= end; i++) {
      list.remove(i);
    }
  }

  public List<Pair<Integer, Integer>> getPairs() {
    List<Integer> data = new ArrayList<>();
    data.addAll(list);
    Collections.sort(data);
    List<Pair<Integer, Integer>> pairs = new ArrayList<>();
    int last = data.get(data.size() - 1);
    int s = -1;
    int e;
    for (int i = 0; i <= last; i++) {
      if (list.contains(i)) {
        if (s == -1) {
          s = i;
        }
        e = i;
        if (!list.contains(i + 1)) {
          Pair<Integer, Integer> p = new Pair<>(s, e);
          pairs.add(p);
          s = -1;
        }
      }
    }
    return pairs;
  }

  public boolean haveGap(int start, int end) {
    boolean b = false;
    for (int i = start; i < end; i++) {
      if (!list.contains(i)) {
        b = true;
        break;
      }
    }
    return b;
  }
}
public class Pair {
  public final int first;
  public final int second;

  public Pair(int first, int second) {
    this.first = first;
    this.second = second;
  }

}
public class ExampleUnitTest {

  @Test public void gapSize() throws Exception {
    GapAwareList gaps = fillGaps();

    gaps.put(0, 2);
    gaps.put(0, 1);
    gaps.put(3, 4);
    gaps.put(6, 8);
    List<Pair<Integer, Integer>> pairs = gaps.getPairs();

    assertEquals(3, pairs.size());
  }

  @Test public void gapFirst() throws Exception {
    GapAwareList gaps = fillGaps();

    gaps.put(0, 2);
    gaps.put(0, 1);
    gaps.put(3, 4);
    gaps.put(6, 8);
    List<Pair<Integer, Integer>> pairs = gaps.getPairs();

    assertTrue(pairs.get(0).first == 0);
    assertTrue(pairs.get(0).second == 4);
  }

  @Test public void gapSecond() throws Exception {
    GapAwareList gaps = fillGaps();
    List<Pair<Integer, Integer>> pairs = gaps.getPairs();

    assertTrue(pairs.get(1).first == 6);
    assertTrue(pairs.get(1).second == 8);
  }

  private GapAwareList fillGaps() {
    GapAwareList gaps = new GapAwareList();
    //add (0,2),(0,1),(3,4),(6,8)
    gaps.put(0, 2);
    gaps.put(3, 4);
    gaps.put(0, 1);
    gaps.put(6, 8);
    gaps.put(13,11);
    gaps.put(13, 13);
    gaps.put(13, 14);

    return gaps;
  }
  @Test public void checkGaps(){
    GapAwareList gaps = fillGaps();
    assertFalse(gaps.haveGap(0,4));
    assertFalse(gaps.haveGap(6, 8));
    assertFalse(gaps.haveGap(6, 7));
    assertTrue(gaps.haveGap(4, 6));
  }
}

Answer 1

来自Java documentation "Restrictions on Generics" :

Cannot Instantiate Generic Types with Primitive Types

Consider the following parameterized type:

class Pair<K, V> {

    private K key;
    private V value;

    public Pair(K key, V value) {
        this.key = key;
        this.value = value;
    }

    // ...
}

When creating a Pair object, you cannot substitute a primitive type for the type parameter K or V:

Pair<int, char> p = new Pair<>(8, 'a');  // compile-time error

You can substitute only non-primitive types for the type parameters K and V:

Pair<Integer, Character> p = new Pair<>(8, 'a');

Note that the Java compiler autoboxes 8 to Integer.valueOf(8) and 'a' to Character('a'):

Pair<Integer, Character> p = new Pair<>(Integer.valueOf(8), new Character('a'));

For more information on autoboxing, see Autoboxing and Unboxing in the Numbers and Strings lesson.