《Android源码设计模式解析和实战》迭代器模式

提供一种方法顺序访问一个容器对象中的各个元素，但又不暴露等于该对象的内部显示。
代码：list

public interface BaseList {
 void add(T t);
void remove(T t);

Iterator iterator();

}
 public class BaseListImpl implements BaseList {
 private List list = new ArrayList<>();
@Override
public void add(T t) {
    list.add(t);
}

@Override
public void remove(T t) {
    list.remove(t);
}

@Override
public Iterator iterator() {
    return new ListIterator<>(list);
}

}
 public interface Iterator {
 boolean hasNext();
T next();

}
 public class ListIterator implements Iterator {
 private List list = new ArrayList<>();
 private int cursor;
public ListIterator(List list) {
    this.list = list;
}

@Override
public boolean hasNext() {
    return cursor != list.size();
}

@Override
public T next() {
    T obj = null;
    if (hasNext()) {
        return list.get(cursor++);
    }
    return obj;
}

}
 

代码：数组

 public interface BaseArray {
 void add(T t, int i);

void remove(int i);

Iterator iterator();

}
 public class BaseArrayImpl implements BaseArray {
private String[] array = new String[3];

@Override
public void add(java.lang.String t, int i) {
    array[i] = t;
}

@Override
public void remove(int i) {

}

@Override
public Iterator iterator() {
    return new ArrayIterator(array);
}

}
 public class ArrayIterator implements Iterator {
 private String[] array;
 private int cursor;
public ArrayIterator(String[] array) {
    this.array = array;
}

@Override
public boolean hasNext() {
    return !(cursor > array.length - 1 || array[cursor] == null);
}

@Override
public String next() {
    if (hasNext()) {
        return array[cursor++];
    }
    return "";
}

}
 

使用

public class MainActivity extends AppCompatActivity {
 private static final String TAG = "MainActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    BaseList baseList = new BaseListImpl<>();
    BaseArray baseArray = new BaseArrayImpl();
    baseList.add("一");
    baseList.add("二");
    baseList.add("三");
    baseArray.add("1", 0);
    baseArray.add("2", 1);
    baseArray.add("3", 2);
    Iterator iterator = baseList.iterator();
    Iterator iterator2 = baseArray.iterator();
    while (iterator.hasNext()) {
        Log.i(TAG, "onCreate: " + iterator.next());
    }
    while (iterator2.hasNext()) {
        Log.i(TAG, "onCreate: " + iterator2.next());
    }
}

}
 

log

 03-13 21:21:15.690 3290-3290/com.lerz.iteratordemo I/MainActivity: onCreate: 一
 03-13 21:21:15.690 3290-3290/com.lerz.iteratordemo I/MainActivity: onCreate: 二
 03-13 21:21:15.690 3290-3290/com.lerz.iteratordemo I/MainActivity: onCreate: 三
 03-13 21:21:15.690 3290-3290/com.lerz.iteratordemo I/MainActivity: onCreate: 1
 03-13 21:21:15.690 3290-3290/com.lerz.iteratordemo I/MainActivity: onCreate: 2
 03-13 21:21:15.690 3290-3290/com.lerz.iteratordemo I/MainActivity: onCreate: 3