how to check the jdk version used to compile a .class file [duplicate]

Answer 1

Btw, the reason that you're having trouble is that the java compiler recognizes two version flags. There is -source 1.5, which assumes java 1.5 level source code, and -target 1.5, which will emit java 1.5 compatible class files. You'll probably want to use both of these switches, but you definitely need -target 1.5; try double checking that eclipse is doing the right thing.

Answer 2

Free JarCheck tool here

Answer 3

You're looking for this on the command line (for a class called MyClass):

On Unix/Linux:

javap -verbose MyClass | grep "major"

On Windows:

javap -verbose MyClass | findstr "major"

You want the major version from the results. Here are some example values:

• 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

Answer 4

You can try jclasslib:

https://github.com/ingokegel/jclasslib

It's nice that it can associate itself with *.class extension.

Answer 5

Does the -verbose flag to your java command yield any useful info? If not, maybe java -X reveals something specific to your version that might help?