Bit operations are java The basic knowledge in the comparison , The calculation speed of bit operation is very fast ,jdk Many source codes use bit operations （ for example ArrayList,HashMap）.

But in the process of daily development , We seldom use bit operations . Compared with its advantages of computing speed , Its readability is not high ” shortcoming “ It seems to be more prominent for ordinary business development .

We prefer to use it directly +,-,*,/ These direct operators .

This article will introduce an application scenario of bit operation in business , I hope I can help you , If there is anything wrong , Welcome to correct .

Introduce the basis of standard mismatch operation , If you are not familiar with the basic concepts of bit operation , Please help yourself first google understand .

One 、 Conventional business marking ideas

In the process of daily business development , Business models are often marked （true/false） The needs of .

for example ：

true Boys ,false Girls say

true It means that there are discounts for participating in the event ,false Indicates that you cannot participate in the event offer

true Super Administrator ,false For ordinary users

.....

Generally speaking, for this kind of demand , We usually use a separate field to represent Domain The state of . As the business grows , More and more logic needs to be marked . Corresponding to Domain/ The fields identified in the table structure will also continue to rise .

@Data
public class User {
    private Long userId;
    private String userName;
    private boolean canLogin;
    private boolean isMale;
    private boolean isAdmin;
    ....
}
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Two 、 Bit operation optimization logic

In order to solve this non A namely B The expansion problem of field identification , We can use bit operations to integrate these fields .

For example, as shown above User Domain, We integrate canLogin,isMale,isAdmin For a field , Think of it as a feature identification （ Set field to featureTag）.

@Data
public class User {
    private Long userId;
    private String userName;
    private int featureTag;
}
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We can define one feature The enumeration of defines what each bit identifies

public enum UserFeatureEnum{
​
    CAN_LOGIN(0),
    IS_MALE(1);
    IS_ADMIN(2);
​
    private int bit;
​
    UserFeatureEnum(int bit) {
        this.bit = bit;
    }
    
    public int getValue() {
        return this.bit;
    }
​
}
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Then we can pass BitUtil Come on check The status of a feature of the current user

public class BitUtil {
    public static int setBit(int options, int bitIndex) {
        int val = 1 << bitIndex;
        return options | val;
    }
​
    public static int unsetBit(int options, int bitIndex) {
        int val = 1 << bitIndex;
        return options & (~ val);
    }
​
    public static boolean isBitSetted(int options, int bitIndex) {
        int val = 1 << bitIndex;
        return (options & val) == val;
    }
​
    public static boolean isBitUnSetted(int options, int bitIndex) {
        int val = 1 << bitIndex;
        return (options & val) == 0;
    }
}
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So if we check user Whether men can do this

boolean isMale = BitUtil.isBitSetted(user.getfeatureTag(),UserFeatureEnum.IS_MALE.getValue());
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Set the current user as female

user.setfeatureTag(BitUtil.unsetBit(user.getfeatureTag(),UserFeatureEnum.IS_MALE.getValue()))
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Set the current user as male

user.setfeatureTag(BitUtil.setBit(user.getfeatureTag(),UserFeatureEnum.IS_MALE.getValue()))
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In this way, we have merged the expanding flag fields , The database can also be identified with only one field Domain The multiple feature.

If you need to add one later feature when , There is no need to modify the table structure , Just add an enumeration value and setting 、 Just judge logic .

Like online projects , Changing the table structure will go a long way DBA Approval process

3、 ... and 、 Comparison of advantages and disadvantages

• Compared with conventional business design , Bit operation is more prominent in space saving and scalability , But the readability is relatively poor .
• stay DB Search on , Conventional design can filter fields directly as conditions , Bit operation requires a bit operation on the condition .
• stay ES Search on , Conventional design can filter fields directly as conditions , Bit operation is not supported , One field needs to be redundant , If Domain Our storage structure is ES, also feature Fields have retrieval requirements , It's better to follow the conventional design .
• If it involves the function of interacting with the client , edition A Of client Supported features , In version B Can't support . Because the client is installed locally , It is impossible to force users to upgrade all the time . So you can use a feature Field , Identify some features supported by the current client , The server parses the returned result . The request parameters are clear and simple , High dynamic .

Four 、 Last

If there is anything wrong in the article , Welcome to correct , Writing is not easy , Give me some advice. , mua ~