分析以下需求,并用代码实现:
(1)有如下代码:
List list = new ArrayList<>();
list.add("a");
list.add("a");
list.add("a");
list.add("b");
list.add("b");
list.add("c");
list.add("d");
list.add("d");
list.add("d");
list.add("d");
list.add("d");
System.out.println(frequency(list, "a")); // 3
System.out.println(frequency(list, "b")); // 2
System.out.println(frequency(list, "c")); // 1
System.out.println(frequency(list, "d")); // 5
System.out.println(frequency(list, "xxx")); // 0
(2)定义方法统计集合中指定元素出现的次数,如"a" 3,"b" 2,"c" 1
package text;
import java.util.ArrayList;
import java.util.List;
public class text02 {
public static void main(String[] args) {
List<String> list = new ArrayList<>();
list.add("a");
list.add("a");
list.add("a");
list.add("b");
list.add("b");
list.add("c");
list.add("d");
list.add("d");
list.add("d");
list.add("d");
list.add("d");
getCount(list);
}
private static void getCount(List list) {
int acount=0;
int bcount=0;
int ccount=0;
int dcount=0;
int xcount=0;
for(int i=0;i<list.size();i++) {
if("a".equals(list.get(i))) {
acount++;
}else if("b".equals(list.get(i))) {
bcount++;
}else if("c".equals(list.get(i))) {
ccount++;
}else if("d".equals(list.get(i))) {
dcount++;
}else if("xxx".equals(list.get(i))) {
xcount++;
}
}
System.out.println("a的个数为:"+acount+",b的个数为:"+bcount+",c的个数为:"+ccount+",d的个数为:"+dcount+",xxx的个数为:"+xcount);
}
}