You can refer to the document https://docs.web3j.io/smart_contracts/ The official document of web3j is written very clearly and can be translated by Google
The first step is to generate the required bin and abi files according to the smart contract.
install install solc
The command npm install -g solc can not use npm, please install the environment by Baidu
After installing solc, generate the bin file and abi file corresponding to the smart contract
solcjs smart contract file path --bin --abi --optimize -o output path
For example: solcjs C:/**/IERC20.sol --bin --abi --optimize -o C:/**/output The corresponding output path will generate bin and abi files (the file name will be longer and can be repeated Naming modification is convenient for future use)
The second step uses the bin and abi files to generate the corresponding java class files
Download web3j https://github.com/web3j/web3j/releases Download the compressed package and decompress it
cmd to open the command line window (cd C:/**/web3j/bin under the bin path decompressed by cd web3j)
generate java file
web3j solidity generate -b bin file -a abi file -p package name -o output path
web3j solidity generate -b C:\**\EIP20Interface.bin -a C:\**\EIP20Interface.abi -p com.wallet.contract -o C:\**\output
Find the corresponding java file in the output path and you can use it