我试图从文本文件中读取一些单词，然后将它们排列成降序数组。
我达到了成功读取单词的地步，将单词存储在数组中，当我继续将其排列为降序形式时，我注意到我的数组也包含一些空值。
当我尝试使用（下面的完整代码）删除空值
<?php if(!empty($work->video_url)): ?>
<iframe ... ></iframe>
<?php endif; ?>
，它仍然没有奏效。
经过一段时间的努力，我觉得我需要一些帮助。
此阶段的代码，文本文件和输出如下：
`
Arrays.stream(w.words).filter(x->x != null).toArray();file.txt是：
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.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Random;
import java.util.Scanner;
import java.util.Set;
import java.util.stream.Collectors;
public class Practise {
private Scanner fp;
private Scanner scanLine;
private String[] words = new String[6] ;
int count;
String temp;
String [][] samewords;
int size;
String[] words_sorted;
public Practise() {
openFile();
readFile();
printa();
}
private void openFile() {
try {
fp = new Scanner(new File ("D:\\workspace\\file.txt"));
}
catch (Exception e) {
System.out.println("File does not exist");
}
}
private void readFile() {
try {
count = 0;
while (fp.hasNextLine()) {
String strLine = fp.nextLine();
scanLine = new Scanner(strLine);
words[count] = scanLine.next();
System.out.println("Here2"+words[count]);
System.out.println();
count++;
}
}
catch (Exception e) {
System.err.print("Error: " + e.getMessage());
}
}
private void printa() {
try (BufferedReader br = new BufferedReader(new FileReader("D:\\workspace\\file.txt"))) {
size = findLongestWords();
samewords = new String[size][size];
String line;
int i = 0;
String [] temp;
while ((line = br.readLine()) != null) {
temp = line.split(",");
for (int j = 0; j < samewords[i].length; j++) {
samewords[i][j] = temp[j];
System.out.println(samewords[i][j]);
}
i++;
}
//System.out.println(answers[1][2]);
} catch (IOException e) {
e.printStackTrace();
}
}
public int findLongestWords() throws FileNotFoundException {
int longest_word = 0;
int current;
BufferedReader sc = new BufferedReader(new FileReader("D:\\workspace\\file.txt"));
String li;
String[] tr;
try {
while ((li = sc.readLine())!= null ) {
tr = li.split(",");
current = tr.length;
if (current > longest_word) {
longest_word = current;
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("\n"+longest_word+"\n");
return longest_word;
}
private String[] sort(String[] string) {
/*Local variables*/
Map<String, Integer> map=new LinkedHashMap<String, Integer>();
Map<String, Integer> mapCopy=new LinkedHashMap<String, Integer>();
int [] lengthsArray=new int[string.length];
String [] sortedStrings=new String[string.length];
int counter1=0;
int counter2=0;
/* Store all the pairs <key,value>
* i.e <string[i],string[i].length>
*/
for(String s:string) {
System.out.println(s);
map.put((String) s, s.length());
lengthsArray[counter1]= s.length();//store all the lengths
counter1++;
}
mapCopy=new LinkedHashMap<String, Integer>(map);//make a copy of map
Arrays.sort(lengthsArray);//sort the array of lengths
/*
* Sort array according to the array of lengths
* by finding the matching value from the map
* then add it to the final string array,and then remove it from the map
*/
for(int item:lengthsArray) {
for(Map.Entry<String, Integer> e:map.entrySet()) {
if(item==e.getValue()) {
sortedStrings[counter2]=e.getKey();
counter2++;
map.remove(e.getKey());
break;
}
}
}
map=mapCopy;
System.out.println(map);//print map
return sortedStrings;
}
public static void main(String[] args) {
Practise w = new Practise();
System.out.println(Arrays.toString(w.words));
w.sort(w.words);
}
}
`
输出是：
ACT,CAT,AT,RAT,PAT,TAT答案 0 :(得分：1)
null是因为您声明的单词数组（预定义大小）。可能你可以改变它并使用ArrayList（因为它可以是动态大小）而不是String数组，这可以帮助你解决。只是为了帮助您，请按照以下更改：
private List<String> words = new ArrayList<>(); /*update below line in readFile() instead of words[count] = scanLine.next();*/
words.add(scanLine.next()); Change method signature sort(List<String> string) //also update below declarations
int[] lengthsArray = new int[string.size()];
String[] sortedStrings = new String[string.size()]; change Arrays.toString(w.words) to just w.words in print statement 希望这会有所帮助。一切都很好看。