Java version number


import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class ClassVersionChecker {
public static void main(String[] args) throws IOException {
for (int i = 0; i < args.length; i++)
checkClassVersion(args[i]);
}

private static void checkClassVersion(String filename) throws IOException {
DataInputStream in = new DataInputStream(new FileInputStream(filename));

int magic = in.readInt();
if (magic != 0xcafebabe) {
System.out.println(filename + " is not a valid class!");
}
int minor = in.readUnsignedShort();
int major = in.readUnsignedShort();
System.out.println(filename + ": " + major + " . " + minor);
in.close();
}
}


1.Compile

javac ClassVersionChecker.java

2.Execute in unix console

find . -name *.class|xargs java -cp /c/tmp ClassVersionChecker|grep 50

where last number is class version

major minor Java platform version
45 3 1.0
45 3 1.1
46 0 1.2
47 0 1.3
48 0 1.4
49 0 1.5
50 0 1.6