Basic Data Types

Basic Data Types

What is the data type? The data type is the definition of data. Each data type will allocate a certain amount of memory space, which is usually

When variables are used together, variables can change in a certain range.

I. Ask questions

Below is a company interview question

byte b1 = 3,b2 = 4,b; b = b1 + b2; b = 3 + 4;

The problem is where the program will go wrong. Why?

The execution result of this program is as follows:

An incompatible type problem occurs in the third line of the Code.

Ii. Problem Analysis

In java, the data type is byte, 1 byte; int (default type); 4 bytes

When declaring variables, b1, b2, and B are of the byte type, and the initial values of b1 and b2 are 3, 4, respectively.

1. Because the default data type in java is int, the sum is automatically converted to int type when b1 + b2 is executed, that is, four bytes,

ThenIn B, because the byte type has only one byte length, the conversion from the int type to the byte type requires three bytes, so

Current data may cause loss errors;

2. This problem may also occur in the third row, but no error is reported because constants are completed in advance During computation.

The reason is as follows:

After writing the code, we need to compile the program first and then run the program. Constant computation is automatically executed during compilation, and

The results have been calculated, so there will be no data loss errors during running. For variables, because the data is not necessarily

When computing is executed, we will find that the data types before and after compilation are inconsistent, and then we will be prompted

It is not difficult to solve this problem. You only need to forcibly convert b1 + b2 to the byte type.

Iii. Summary

The data types in java are automatically compatible with the upstream. If all data types are declared as long, no errors will occur.

1. byte, short, char-int-long-float-double conversion from small to large

2. byte, short, and char do not convert each other

I was not so concerned about some things with special details before. problems may occur when they are actually used.