A class file is a set of binary streams that are based on 8-bit bytes, and each data item is tightly arranged in a class file with no delimiters in the middle. When a data item that requires more than 8 bytes is encountered, it is stored in a number of 8-bit bytes in the way it was before the high-bit.
According to the Java Virtual Machine specification, the class file format is stored in a pseudo-structure similar to the C language structure, with only two data types: unsigned number and table. Unsigned numbers are based on data types, with U1, U2, U4, U8, respectively, code 1 bytes, 2 bytes, 4 bytes, 8 bytes of unsigned numbers, unsigned numbers can be used to describe numbers, index references, quantity values, or string values that are composed of UTF-8 encodings. A table is a composite data type consisting of multiple symbols or other tables as data items, all of which habitually end with "_info". Tables are used to describe the hierarchical structure of a complex, and the entire class file is essentially a table, which consists of the following data items:
Whether it is an unsigned number or a table, when you need to describe the same type but a variable number of data, often use a predecessor capacity counter plus a number of consecutive data items, this time called a series of continuous data of a certain type of a set.
An in-depth understanding of Java Virtual Machine notes---class file structure overview
