Java如何计算数组中数字的出现？
package org.nhooo.example.lang;
import java.util.HashMap;
import java.util.Map;
public class NumberOccurrenceInArray {
public static void main(String[] args) {
int[] numbers = new int[]{1, 8, 3, 4, 3, 2, 5, 7, 3, 1, 4, 5, 6, 4, 3};
Map<Integer, Integer> map = new HashMap<>();
for (int key : numbers) {
if (map.containsKey(key)) {
int occurrence = map.get(key);
occurrence++;
map.put(key, occurrence);
} else {
map.put(key, 1);
}
}
for (Integer key : map.keySet()) {
int occurrence = map.get(key);
System.out.println(key + " occur " + occurrence + " time(s).");
}
}
}结果是：
1 occur 2 time(s). 2 occur 1 time(s). 3 occur 4 time(s). 4 occur 3 time(s). 5 occur 2 time(s). 6 occur 1 time(s). 7 occur 1 time(s). 8 occur 1 time(s).