问题

代码

主程序

package Chapter3; /** * * @author Crissu * 交集和并集 */ public class Three_Four {  public static void main(String[] args) {  // TODO Auto-generated method stub //创建list1 MyArrayList<Integer> list1 = new MyArrayList<>(); list1.add(1); list1.add(3); list1.add(5); list1.add(7); list1.add(9); // 创建list2 MyArrayList<Integer> list2 = new MyArrayList<>(); list2.add(1); list2.add(2); list2.add(5); list2.add(7); list2.add(8); list2.add(9); // 交集 MyArrayList<Integer> mergeList; mergeList = JiaoJi(list1, list2); // 输出 System.out.println("交集"); for(int i=0; i<mergeList.size(); i++) {  System.out.print(mergeList.get(i)); } System.out.println(); // 并集 mergeList = BingJi(list1, list2); // 输出 System.out.println("并集"); for(int i=0; i<mergeList.size(); i++) {  System.out.print(mergeList.get(i)); } System.out.println(); } /** * 交集 * @param list1 * @param list2 * @return */ private static MyArrayList<Integer> JiaoJi(MyArrayList<Integer> list1, MyArrayList<Integer> list2) {  // TODO Auto-generated method stub MyArrayList<Integer> mergeList = new MyArrayList<>(); int index1 = 0; int index2 = 0; int v1, v2; while(index1 < list1.size() && index2 < list2.size()) {  v1 = list1.get(index1); v2 = list2.get(index2); if(v1 < v2) {  index1++; }else if(v1 > v2) {  index2++; }else {  mergeList.add(v1); index1++; index2++; } } return mergeList; } /** * 并集 * @param list1 * @param list2 * @return */ private static MyArrayList<Integer> BingJi(MyArrayList<Integer> list1, MyArrayList<Integer> list2) {  // TODO Auto-generated method stub MyArrayList<Integer> mergeList = new MyArrayList<>(); int index1 = 0; int index2 = 0; int v1, v2; while(index1 < list1.size() && index2 < list2.size()) {  v1 = list1.get(index1); v2 = list2.get(index2); if(v1 < v2) {  mergeList.add(v1); index1++; }else if(v1 > v2) {  mergeList.add(v2); index2++; }else {  mergeList.add(v1); index1++; index2++; } } // 处理剩下的 if(index1 == list1.size()) {  //说明list2还有剩下 for(; index2<list2.size(); index2++) {  v2 = list2.get(index2); mergeList.add(v2); } } if(index2 == list2.size()) {  //说明list1还有剩下 for(; index1<list1.size(); index1++) {  v1 = list1.get(index1); mergeList.add(v1); } } return mergeList; } } 

MyArrayList

package Chapter3; import java.util.Iterator; /** * * @author Crissu * * @param <AnyType> */ public class MyArrayList<AnyType> implements Iterable<AnyType> {  private static final int DEFAULT_CAPACITY = 10; private int theSize; private AnyType[] theItems; public MyArrayList() {  doClear(); } public void clear() {  clear(); } public int size() {  return theSize; } public boolean isEmpty() {  return size()==0; } public void trimToSize() {  ensureCapacity(size()); } public AnyType get(int idx) {  if(idx < 0 || idx >= size()) {  throw new ArrayIndexOutOfBoundsException(); } return theItems[idx]; } public AnyType set(int idx, AnyType newVal) {  if(idx < 0 || idx >= size()) {  throw new ArrayIndexOutOfBoundsException(); } AnyType old = theItems[idx]; theItems[idx] = newVal; return old; } public boolean add(AnyType x) {  add(size(), x); return true; } public void add(int idx, AnyType x) {  if(theItems.length == size()) {  ensureCapacity(size()*2+1); } for(int i = theSize; i>idx; i--) {  theItems[i] = theItems[i-1]; } theItems[idx] = x; theSize++; } public AnyType remove(int idx) {  AnyType removedItem = theItems[idx]; for(int i=idx; i<size()-1; i++) {  theItems[i] = theItems[i++]; } theSize--; return removedItem; } private void doClear() {  // TODO Auto-generated method stub theSize = 0; ensureCapacity(DEFAULT_CAPACITY); } private void ensureCapacity(int newCapacity) {  // TODO Auto-generated method stub if(newCapacity < theSize) {  return; } AnyType[] old = theItems; theItems = (AnyType [])new Object[newCapacity]; for(int i=0; i< size(); i++) {  theItems[i] = old[i]; } } public java.util.Iterator<AnyType> iterator(){  return new ArrayListIterator(); } private class ArrayListIterator implements java.util.Iterator<AnyType>{  private int current = 0; @Override public boolean hasNext() {  // TODO Auto-generated method stub return current<size(); } @Override public AnyType next() {  // TODO Auto-generated method stub if(!hasNext()) throw new java.util.NoSuchElementException(); return theItems[current++]; } public void remove() {  MyArrayList.this.remove(--current); } } } 

结果