Array and collection performance comparison

Array and collection performance comparison , The set optimizes and classifies the data structure into ：ArrayList、Map wait , How about their performance with arrays of basic types . Time is better than theory ： read 、 Write two aspects .

Write performance comparison

public class ArrayTest {
    
    public static void main(String[] args) {
    
        //  Yes jvm、cup Preheat 
        int temp=0;
        for (int i=0;i<1000000;i++){
    
            temp+=i;
        }
        System.out.println(temp);

        String[] arr = new String[1000000];
        Collection<String> coll = new ArrayList<>();
        long start = System.currentTimeMillis();
        for (int i = 0; i < 1000000; i++) {
    
            arr[i] = i + "";
        }
        System.out.println(" Array 100w Assignment time ：" + (System.currentTimeMillis() - start));
        start = System.currentTimeMillis();
        for (int i = 0; i < 1000000; i++) {
    
            coll.add(i + "");
        }
        System.out.println(" aggregate 100w Assignment time ：" + (System.currentTimeMillis() - start));
    }
}

result ：

1783293664
 Array 100w Assignment time ：39
 aggregate 100w Assignment time ：44

Regardless of the order , Normal writing or basic type performance is fast

Reading performance comparison

public class ArrayTest02 {
    
    public static void main(String[] args) {
    
        //  Yes jvm、cup Preheat 
        int temp = 0;
        for (int i = 0; i < 1000000; i++) {
    
            temp += i;
        }
        System.out.println(temp);

        String[] arr = new String[1000000];
        Collection<String> coll = new ArrayList<>();
        long start = 0;
        start = System.currentTimeMillis();
        for (int i = 0; i < 1000000; i++) {
    
            coll.add(i + "");
        }
        System.out.println(" aggregate 100w Assignment time ：" + (System.currentTimeMillis() - start));

        start = System.currentTimeMillis();
        for (int i = 0; i < 1000000; i++) {
    
            arr[i] = i + "";
        }
        System.out.println(" Array 100w Assignment time ：" + (System.currentTimeMillis() - start));

        List<String> read = new ArrayList<>();
        read.add("5");
        read.add("999999");
        read.add("439999");
        read.add("666666");

        start = System.currentTimeMillis();
        for (String find : read)
            if(coll.contains(find)){
    
                temp++;
            }
        System.out.println(" aggregate 100w Random reading takes time ：" + (System.currentTimeMillis() - start));

        start = System.currentTimeMillis();
        for (String find : read)
            for (int i = 0; i < arr.length; i++) {
    
                if (find.equals(arr[i])) {
    
                    temp++;
                    break;
                }
            }
        System.out.println(" Array 100w Random reading takes time ：" + (System.currentTimeMillis() - start));
    }
}

Results a ：

1783293664
 aggregate 100w Assignment time ：50
 Array 100w Assignment time ：59
 aggregate 100w Random reading takes time ：15
 Array 100w Random reading takes time ：13

Structure II ：

1783293664
 aggregate 100w Assignment time ：47
 Array 100w Assignment time ：61
 Array 100w Random reading takes time ：16
 aggregate 100w Random reading takes time ：15

It's not hard to see. , Successively implement and jvm、CPU It's about scheduling , No matter what , Basic arrays are preferred , After all, the bottom layer of the set is the array implementation

Conclusion

Data volume 100w There is no performance gap at level , You can choose collection storage , Because there are a lot of interface methods , Convenient to call .
On Performance square accounts in every detail You can choose the basic type array .