java集合：线性表

MyList

public interface MyList<E> {  /** Add a new element at the end of this list */  public void add(E e);  /** Add a new element at the specified index in this list */  public void add(int index, E e);  /** Clear the list */  public void clear();  /** Return true if this list contains the element */  public boolean contains(E e);  /** Return the element from this list at the specified index */  public E get(int index);  /** Return the index of the first matching element in this list.   *  Return -1 if no match. */  public int indexOf(E e);  /** Return true if this list contains no elements */  public boolean isEmpty();  /** Return the index of the last matching element in this list   *  Return -1 if no match. */  public int lastIndexOf(E e);  /** Remove the first occurrence of the element o from this list.   *  Shift any subsequent elements to the left.   *  Return true if the element is removed. */  public boolean remove(E e);  /** Remove the element at the specified position in this list   *  Shift any subsequent elements to the left.   *  Return the element that was removed from the list. */  public E remove(int index);  /** Replace the element at the specified position in this list   *  with the specified element and returns the new set. */  public Object set(int index, E e);  /** Return the number of elements in this list */  public int size();}

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• MyAbstractList

public abstract class MyAbstractList<E> implements MyList<E> {  protected int size = 0; // The size of the list  /** Create a default list */  protected MyAbstractList() {  }  /** Create a list from an array of objects */  protected MyAbstractList(E[] objects) {    for (int i = 0; i < objects.length; i++)      add(objects[i]);  }  /** Add a new element at the end of this list */  public void add(E e) {    add(size, e);  }  /** Return true if this list contains no elements */  public boolean isEmpty() {    return size == 0;  }  /** Return the number of elements in this list */  public int size() {    return size;  }  /** Remove the first occurrence of the element o from this list.   *  Shift any subsequent elements to the left.   *  Return true if the element is removed. */  public boolean remove(E e) {    if (indexOf(e) >= 0) {      remove(indexOf(e));      return true;    }    else      return false;  }}

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• 数组线性表

public class MyArrayList<E> extends MyAbstractList<E> {  public static final int INITIAL_CAPACITY = 16;  private E[] data = (E[])new Object[INITIAL_CAPACITY];  /** Create a default list */  public MyArrayList() {  }  /** Create a list from an array of objects */  public MyArrayList(E[] objects) {    for (int i = 0; i < objects.length; i++)      add(objects[i]); // Warning: don抰 use super(objects)!   }  /** Add a new element at the specified index in this list */  public void add(int index, E e) {    ensureCapacity();    // Move the elements to the right after the specified index    for (int i = size - 1; i >= index; i--)      data[i + 1] = data[i];    // Insert new element to data[index]    data[index] = e;    // Increase size by 1    size++;  }  /** Create a new larger array, double the current size */  private void ensureCapacity() {    if (size >= data.length) {      E[] newData = (E[])(new Object[size * 2 + 1]);      System.arraycopy(data, 0, newData, 0, size);      data = newData;    }  }  /** Clear the list */  public void clear() {    data = (E[])new Object[INITIAL_CAPACITY];    size = 0;  }  /** Return true if this list contains the element */  public boolean contains(E e) {    for (int i = 0; i < size; i++)      if (e.equals(data[i])) return true;    return false;  }  /** Return the element from this list at the specified index */  public E get(int index) {    return data[index];  }  /** Return the index of the first matching element in this list.   *  Return -1 if no match. */  public int indexOf(E e) {    for (int i = 0; i < size; i++)      if (e.equals(data[i])) return i;    return -1;  }  /** Return the index of the last matching element in this list   *  Return -1 if no match. */  public int lastIndexOf(E e) {    for (int i = size - 1; i >= 0; i--)      if (e.equals(data[i])) return i;    return -1;  }  /** Remove the element at the specified position in this list   *  Shift any subsequent elements to the left.   *  Return the element that was removed from the list. */  public E remove(int index) {    E e = data[index];    // Shift data to the left    for (int j = index; j < size - 1; j++)      data[j] = data[j + 1];    data[size - 1] = null; // This element is now null    // Decrement size    size--;    return e;  }  /** Replace the element at the specified position in this list   *  with the specified element. */  public E set(int index, E e) {    E old = data[index];    data[index] = e;    return old;  }  /** Override toString() to return elements in the list */  public String toString() {    StringBuilder result = new StringBuilder("[");    for (int i = 0; i < size; i++) {      result.append(data[i]);      if (i < size - 1) result.append(", ");    }    return result.toString() + "]";  }  /** Trims the capacity to current size */  public void trimToSize() {    if (size != data.length) { // If size == capacity, no need to trim      E[] newData = (E[])(new Object[size]);      System.arraycopy(data, 0, newData, 0, size);      data = newData;    }  }}

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• 测试

public class TestList {  public static void main(String[] args) {    // Create a list    MyList<String> list = new MyArrayList<String>();    // Add elements to the list    list.add("America"); // Add it to the list    System.out.println("(1) " + list);    list.add(0, "Canada"); // Add it to the beginning of the list    System.out.println("(2) " + list);    list.add("Russia"); // Add it to the end of the list    System.out.println("(3) " + list);    list.add("France"); // Add it to the end of the list    System.out.println("(4) " + list);    list.add(2, "Germany"); // Add it to the list at index 2    System.out.println("(5) " + list);    list.add(5, "Norway"); // Add it to the list at index 5    System.out.println("(6) " + list);    // Remove elements from the list    list.remove("Canada"); // Same as list.remove(0) in this case    System.out.println("(7) " + list);    list.remove(2); // Remove the element at index 2    System.out.println("(8) " + list);    list.remove(list.size() - 1); // Remove the last element    System.out.println("(9) " + list);  }}