今天在群里又有一个朋友问到了这样一个练习，我索性将代码贴到这里，下次需要的朋友可以来这里看。
用到知识点：数组、集合、IO流
问题描述：在如下图所示的一个txt文件中读取数据到内存，然后统计列除过0的各个数字的个数（放入Map）并按照列的数据大小排序。
代码：
package com.test;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.TreeMap;
public class Week {
private static List<int[]> readFile1(String fileName) {
List<int[]> list = new ArrayList<int[]>();
String line = "";
int[] arr;
FileReader fr = null;
BufferedReader br = null;
try {
File file = new File(fileName);
fr = new FileReader(file);
br = new BufferedReader(fr);
while (br.ready()) {
line = br.readLine();
String[] data = line.split(",");
arr = new int[data.length];
for (int j = 0; j < data.length; j++) {
arr[j] = Integer.parseInt(data[j]);
}
list.add(arr);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally{
if(br != null){
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(fr != null){
try {
fr.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return list;
}
private static int[][] revertData(List<int[]> data) {
int maxCol = 0;
for (int i = 0; i < data.size(); i++) {
if (data.get(i).length > maxCol) {
maxCol = data.get(i).length;
}
}
int[][] arrs = new int[maxCol][data.size()];
for (int i = 0; i < data.size(); i++) {
int[] arr = data.get(i);
for (int j = 0; j < arr.length; j++) {
arrs[j][i] = arr[j];
}
}
return arrs;
}
private static void countKeyNum(int[][] arrs) {
TreeMap<Integer, Integer> map;
for (int i = 0; i < arrs.length; i++) {
map = new TreeMap<Integer, Integer>(new Comparator<Integer>() {
@Override
public int compare(Integer o1, Integer o2) {
return o1.compareTo(o2);
}
});
for (int j = 0; j < arrs[i].length; j++) {
if (arrs[i][j] == 0)
continue;
if (map.containsKey(arrs[i][j])) {
map.put(arrs[i][j], map.get(arrs[i][j]) + 1);
} else {
map.put(arrs[i][j], 1);
}
}
System.out.println(map);
}
}
public static void main(String args[]) {
List<int[]> data = readFile1("week.txt");
int[][] arrs = revertData(data);
countKeyNum(arrs);
}
}
部分运行结果：