问题
I saw this list of major version numbers for Java in another post:
- Java 1.2 uses major version 46
- Java 1.3 uses major version 47
- Java 1.4 uses major version 48
- Java 5 uses major version 49
- Java 6 uses major version 50
- Java 7 uses major version 51
- Java 8 uses major version 52
- Java 9 uses major version 53
- Java 10 uses major version 54
- Java 11 uses major version 55
- Java 12 uses major version 56
- Java 13 uses major version 57
- Java 14 uses major version 58
References:
https://blogs.oracle.com/darcy/entry/source_target_class_file_version https://en.wikipedia.org/wiki/Java_class_file#General_layout
回答1:
These come from the class version. If you try to load something compiled for java 6 in a java 5 runtime you'll get the error, incompatible class version, got 50, expected 49. Or something like that.
See here in byte offset 7 for more info.
Additional info can also be found here.
回答2:
I found a list of Java class file versions on the Wikipedia page that describes the class file format:
http://en.wikipedia.org/wiki/Java_class_file#General_layout
Under byte offset 6 & 7, the versions are listed with which Java VM they correspond to.
回答3:
If you're having some problem about "error compiler of class file", it's possible to resolve this by changing the project's JRE to its correspondent through Eclipse.
- Build path
- Configure build path
- Change library to correspondent of table that friend shows last.
- Create "jar file" and compile and execute.
I did that and it worked.
回答4:
If you have a class file at build/com/foo/Hello.class, you can check what java version it is compiled at using the command:
javap -v build/com/foo/Hello.class | grep "major"
Example usage:
$ javap -v build/classes/java/main/org/aguibert/liberty/Book.class | grep major
major version: 57
According to the table in the OP, major version 57 means the class file was compiled to JDK 13 bytecode level
来源：https://stackoverflow.com/questions/9170832/list-of-java-class-file-format-major-version-numbers