See the created string objects in the system

Question

Hi all, I want to see the values of the created string objects in the system. To do so, I override the String.class by using Xbootclasspath option. In my new overriding class I modified constructors of String.class by adding the line System.out.println(value) to each, such that

public String() {
 this.offset = 0;
 this.count = 0;
 this.value = new char[0];
 System.out.println(value);
}

But I got the error,

Error occurred during initialization of VM
java.lang.ExceptionInInitializerError
 at java.lang.Runtime.loadLibrary0(Runtime.java:819)
 at java.lang.System.loadLibrary(System.java:1030)
 at java.lang.System.initializeSystemClass(System.java:1077)
Caused by: java.lang.NullPointerException
 at java.lang.String.<init>(String.java:219)
 at java.lang.StringBuilder.toString(StringBuilder.java:430)
 at java.io.File.<clinit>(File.java:167)
 at java.lang.Runtime.loadLibrary0(Runtime.java:819)
 at java.lang.System.loadLibrary(System.java:1030)
 at java.lang.System.initializeSystemClass(System.java:1077)

If anyone can point me on how to see the created string objects, I would be really glad.

Answer 1

It means System.out is null. In fact while loading some classes, a new String is created and the System.out field has not been yet initialized.

You should deffer the printing, or may be just keep information about created string in a private field and latter have a look on this field using debugger for example.

Answer 2

I guess there are Strings being created before System.out is initialized. If you can ignore these Strings in the early program phase, maybe you could try something like:

if (System.out != null) 
  System.out.println(value);