Pair的使用

public class Pair<F, S> {
    public final F first;
    public final S second;

    /**
     * Constructor for a Pair.
     *
     * @param first the first object in the Pair
     * @param second the second object in the pair
     */
    public Pair(F first, S second) {
        this.first = first;
        this.second = second;
    }

    /**
     * Checks the two objects for equality by delegating to their respective
     * {@link Object#equals(Object)} methods.
     *
     * @param o the {@link Pair} to which this one is to be checked for equality
     * @return true if the underlying objects of the Pair are both considered
     *         equal
　　　* 这里需要注意一下：如果此处传进来的参数不是Pair类型，就直接返回false。
　　  * 　　　　　　　　　如果参数是Pair类型，在近一步比较。下面会近一步讲解。
     */
    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Pair)) {
            return false;
        }
        Pair<?, ?> p = (Pair<?, ?>) o;
        return Objects.equal(p.first, first) && Objects.equal(p.second, second);
    }

    /**
     * Compute a hash code using the hash codes of the underlying objects
     *
     * @return a hashcode of the Pair
　　  * ^ 按位异或 若参加运算的两个二进制位值相同,则为0，不同否则为1
     */
    @Override
    public int hashCode() {
        return (first == null ? 0 : first.hashCode()) ^ (second == null ? 0 : second.hashCode());
    }

    /**
     * Convenience method for creating an appropriately typed pair.
     * @param a the first object in the Pair
     * @param b the second object in the pair
     * @return a Pair that is templatized with the types of a and b
     */
    public static <A, B> Pair <A, B> create(A a, B b) {
        return new Pair<A, B>(a, b);
    }
}

public class PairActivity extends Activity {
    private final String TAG = "PairActivity.class";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Integer a  = 3;
        Integer b  = 3;
        Log.e("TAG", "--a.equals(b)----"+a.equals(b));// true --- Integer类型的equals方法比较的是数值


        Pair pair = new Pair(1, 2);//第一种创建方式
        Log.e("TAG", pair.first.toString());// 1
        Log.e("TAG", pair.second.toString());// 2
        Log.e("TAG", pair.equals("1") + "");// false
        Log.e("TAG", pair.equals(1) + "");// false
        Log.e("TAG", "------------------------");


        Pair pair2 = Pair.create("1", 2);//第二种创建方式
        Log.e("TAG", pair2.first.equals("1") + "");// true --- String类型的equals方法比较的是内容
        Log.e("TAG", pair2.first.equals(1) + "");// false
        Log.e("TAG", pair2.second.equals(2) + "");// true --- Integer类型的equals方法比较的是数值
        Log.e("TAG", pair.equals(1) + "");// false
        Log.e("TAG", pair.equals("1") + "");// false
        Log.e("TAG", "------------------------");


        Log.e("TAG", pair.equals(pair2) + "");// false
        Log.e("TAG", pair.equals(pair) + "");// true
    }
}　　

 /**
   * Null-safe equivalent of {@code a.equals(b)}.
   */
  public static boolean equals(Object a, Object b) {
    return (a == null) ? (b == null) : a.equals(b);
  }

@Override 
public boolean equals(Object other) {
        if (other == this) {
          return true;
        }
        if (other instanceof String) {
            String s = (String)other;
            int count = this.count;
            if (s.count != count) {
                return false;
            }
            // TODO: we want to avoid many boundchecks in the loop below
            // for long Strings until we have array equality intrinsic.
            // Bad benchmarks just push .equals without first getting a
            // hashCode hit (unlike real world use in a Hashtable). Filter
            // out these long strings here. When we get the array equality
            // intrinsic then remove this use of hashCode.
            if (hashCode() != s.hashCode()) {
                return false;
            }
            for (int i = 0; i < count; ++i) {
                if (charAt(i) != s.charAt(i)) {
                    return false;
                }
            }
            return true;
        } else {
            return false;
        }
    }

 @Override
 public boolean equals(Object o) {
     return (o instanceof Integer) && (((Integer) o).value == value);
 }