华为OD机考题(基础API)

基础API

字典排序

List<String> list=new ArrayList();
//add list member
Arrays.sort(list);List<Map<String,Integer>> list=new ArrayList();
//add list member
Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {@Overridepublic int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2{return o2.getValue()-o1.getValue();}
});

进制转换

Integer.parseInt(hexString, 16)//16进制转10进制

Integer.toBinaryString(num);//十进制转二进制

int decimal = Integer.parseInt(binaryString, 2);//二进制转10进制

>> 有符号右移

>>>无符号右移

bit处理​​​​​​

​Integer.bitCount(n);//二进制中1的个数

字典排序示例:

package huaweiod;import java.util.*;public class Test{public static void main(String[] args) throws Exception{Map<String,Map<String,Integer>> map=new HashMap();Map<String,Integer> map1=new HashMap();map1.put("004",160);map1.put("003",150);map1.put("002",150);map1.put("001",160);map1.put("005",150);map.put("02",map1);Map<String,Integer> map2=new HashMap();map2.put("003",130);map2.put("004",140);map.put("01",map2);Set<String> classNum=map.keySet();Object[] array=classNum.toArray();Arrays.sort(classNum.toArray());for(Object o:array){System.out.println("class:"+o);HashMap<String,Integer> tempMap=(HashMap)map.get(o);List<Map.Entry<String,Integer>> list=new ArrayList(tempMap.entrySet());Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {@Overridepublic int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {return o2.getValue()-o1.getValue();}});for(Map.Entry<String,Integer> entry:list){System.out.println(entry.getKey()+":"+entry.getValue());}}}
}