$ cat BadClassLiteral.java
public class BadClassLiteral {
    public static void method() {
        Class c1 = this.class;
        Class c2 = "".class;
        Class c3 = 0 .class;
        Class c4 = null.class;
        Object x;
        Class c5 = x.toString().class;
    }
}

Compiling this code with java 8 gives the output:

$ ~/jdk8/bin/javac -XDrawDiagnostics BadClassLiteral.java
BadClassLiteral.java:3:25: compiler.err.expected: token.identifier
BadClassLiteral.java:4:23: compiler.err.expected: token.identifier
BadClassLiteral.java:5:23: compiler.err.expected: token.identifier
BadClassLiteral.java:6:25: compiler.err.expected: token.identifier
BadClassLiteral.java:8:33: compiler.err.expected: token.identifier
5 errors

Compiling this code with java 9 gives the output:

$ ~/jdk9/bin/javac -XDrawDiagnostics BadClassLiteral.java
BadClassLiteral.java:3:25: compiler.err.expected: token.identifier
BadClassLiteral.java:3:30: compiler.err.expected: token.identifier
BadClassLiteral.java:4:23: compiler.err.expected: token.identifier
BadClassLiteral.java:4:28: compiler.err.expected: token.identifier
BadClassLiteral.java:5:23: compiler.err.expected: token.identifier
BadClassLiteral.java:5:28: compiler.err.expected: token.identifier
BadClassLiteral.java:6:25: compiler.err.expected: token.identifier
BadClassLiteral.java:6:30: compiler.err.expected: token.identifier
BadClassLiteral.java:8:33: compiler.err.expected: token.identifier
BadClassLiteral.java:8:38: compiler.err.expected: token.identifier
BadClassLiteral.java:10:2: compiler.err.premature.eof
11 errors

Every duplicated line of these cases is about just one error - incorrect usage of 'class' literal. But java 9 produces two error messages instead of one. It makes the situation unclear.

Also, theextra error at th end is absolutely wrong in this place because the code syntactically correct.