Java signature refers to the digital signature of code to ensure the reliability and integrity of code source code. Java signatures are divided into two types: self-signature and certificate signature. Self-signing is simple, and only Java keytool is needed to generate a signing certificate, but the trust is low. Certificate signing usually requires purchasing or obtaining a digital signature certificate, which is verified by Java keytool tool, which is more reliable.

Java signature is very important for developers, because it can enhance the credibility of the program. Users are prone to security problems when downloading and installing software, and digital signature can prove that the software was released by the developer and has not been modified or tampered with. At the same time, digital signature can also ensure the integrity of the software, and users can use the software with confidence.

Even if a Java program has been signed, it may still be attacked by malicious code. This is because hackers may steal digital signature certificates and forge signatures in order to execute malicious code normally. Therefore, developers need to strengthen the security of Java code and avoid the abuse and disclosure of signing certificates to ensure the security of the code.