Disabling compile-time dependency checking when compiling Java classes

Question

Consider the following two Java classes:

a.) class Test { void foo(Object foobar) { } }

b.) class Test { void foo(pkg.not.in.classpath.FooBar foobar) { } }
         


        

Answer 1

Can you give any example for which it would be technically impossible to generate a valid Java class file without performing compile time dependency checking?

Consider this code:

public class GotDeps {
  public static void main(String[] args) {
    int i = 1;
    Dep.foo(i);
  }
}

If the target method has the signature public static void foo(int n), then these instructions will be generated:

public static void main(java.lang.String[]);
  Code:
   0:   iconst_1
   1:   istore_1
   2:   iload_1
   3:   invokestatic    #16; //Method Dep.foo:(I)V
   6:   return

If the target method has the signature public static void foo(long n), then the int will be promoted to a long prior to the method invocation:

public static void main(java.lang.String[]);
  Code:
   0:   iconst_1
   1:   istore_1
   2:   iload_1
   3:   i2l
   4:   invokestatic    #16; //Method Dep.foo:(J)V
   7:   return

In this case, it would not be possible to generate the invocation instructions or how to populate the CONSTANT_Methodref_info structure referred to in the class constant pool by the number 16. See the class file format in the VM spec for more details.