第三周作业——冒泡排序和归并排序

1. 排序。对文件 largeW.txt（下载链接）中的数据，编程实现冒泡排序（方法名：bubbleSort） 与 归并排序（mergeSort），把排序后的结果分别保存到largeW_bubble.txt 和 largeW_merge.txt 中，把两种排序结果的运行时间输出到屏幕中（发博文时把运行时间的截图作为运行结果提交）。

注：由于源文件太大，进行冒泡排序时间较长，故取了一部分数据进行测试

package homework;import java.io.*;import java.util.*;public class ch04{public static void main(String[] args) throws IOException {/*--------------------------------------冒泡排序-------------------------------------------*/ArrayList<Integer> aList=getData();Object [] dataSeqBubble=aList.toArray();long bubbleBeginTime=System.currentTimeMillis();Object [] infile=bubbleSort(dataSeqBubble);long bubbleEndTime=System.currentTimeMillis();System.out.println("冒泡排序---用时为："+(bubbleEndTime-bubbleBeginTime)+"毫秒");/*--------------------------------------归并排序-------------------------------------------*/ArrayList<Integer> aList2=getData();//将aList2转换为Object数组Object [] dataSeqMerge=aList2.toArray();int arraylength=dataSeqMerge.length;Object [] newarray=new Object[arraylength];long mergeBeginTime=System.currentTimeMillis();mergeSort(dataSeqMerge, newarray, 0, arraylength-1);long mergeEndTime=System.currentTimeMillis();System.out.print("归并排序---用时为："+(mergeEndTime-mergeBeginTime)+"毫秒");}//获取数据,返回一个ArrayListpublic static ArrayList<Integer> getData() throws IOException{FileReader fis=new FileReader("2e2.txt");char[] readNum=new char[7];int num=0;ArrayList<Integer>  al=new ArrayList<Integer>();while ((num=fis.read(readNum))!=-1) {              String dataStoreString= new String(readNum,0,num).trim();int dataStore=Integer.parseInt(dataStoreString);al.add(dataStore);}fis.close();return al;}//冒泡排序public static Object[]  bubbleSort(Object [] dataArrayList)  {int temp=0;for (int i = 0; i < dataArrayList.length-1; i++) {for (int j = 0; j < dataArrayList.length-1-i; j++) {if ((Integer)dataArrayList[j]>(Integer)dataArrayList[j+1]) {temp=(Integer)dataArrayList[j];dataArrayList[j]=dataArrayList[j+1];dataArrayList[j+1]=temp;}}}return dataArrayList;}//一次归并算法public static void merge(int first,int mid,int last,Object firstArray[],Object finalArray[]){int i=first;int j=mid+1;//最终数组开始位置int k=first;while(i<=mid  && j<=last){if ((Integer)firstArray[i] <= (Integer)firstArray[j]) {finalArray[k++]=firstArray[i++];}else {finalArray[k++]=firstArray[j++];}}if (i<=mid) {while (i<=mid) {finalArray[k++]=firstArray[i++];}}else{while (j<=last) {finalArray[k++]=firstArray[j++];}}}//归并排序public static void mergeSort(Object firstArray[],Object finalArray[],int first,int last){if(first==last)  //待排序只有一个记录，递归结束finalArray[first]=firstArray[first];else {int mid=(first+last)/2;mergeSort(firstArray, finalArray, first, mid);//对数组前半段进行排序mergeSort(firstArray, finalArray, mid+1, last);//对数组前半段进行排序merge(first, mid, last, finalArray, firstArray);//合并}}}