It`s OK in IntelliJ IDEA. but not here.
output:
java.lang.NullPointerException
at zh.codegym.task.task09.task0930.Solution.main(Solution.java:17)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
package zh.codegym.task.task09.task0930;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
/*
有关算法的任务
*/
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
ArrayList<String> list = new ArrayList<String>();
while (true) {
String s = reader.readLine();
if (s.isEmpty()) break;
list.add(s);
}
String[] array = list.toArray(new String[list.size()]);
sort(array);
for (String x : array) {
System.out.println(x);
}
}
public static void sort(String[] array) {
// 在此编写你的代码
for (int i = 0; i < array.length; i++) {
for (int j = i + 1; j < array.length - 1; j++) {
if (isNumber(array[i]) && isNumber(array[j])) {
if (Integer.parseInt(array[i]) < Integer.parseInt(array[j])) {
String temp = array[i];
array[i] = array[j];
array[j] = temp;
}
} else if (!isNumber(array[i]) && !isNumber(array[j])) {
if (isGreaterThan(array[i], array[j])) {
String temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
}
}
// 字符串比较方法：‘a’大于‘b’
public static boolean isGreaterThan(String a, String b) {
return a.compareTo(b) > 0;
}
// 传递的字符串是数字吗？
public static boolean isNumber(String s) {
if (s.length() == 0) return false;
char[] chars = s.toCharArray();
for (int i = 0; i < chars.length; i++) {
char c = chars[i];
if ((i != 0 && c == '-') // 字符串包含连字符
|| (!Character.isDigit(c) && c != '-') // 或不是数字并且不以连字符开头
|| (i == 0 && c == '-' && chars.length == 1)) // 或为单个连字符
{
return false;
}
}
return true;
}
}