Search code examples
javabytecode

Not getting extends java.lang.Object in bytecode. so why compiler is not adding it in newer version of java?

I have simple code as below 

package prashant;
public class CheckObject {
}

I used javap -c CheckObject and got below bytecode :

 Compiled from "CheckObject.java"
 public class prashant.CheckObject {
 public prashant.CheckObject();
 Code:
   0: aload_0       
   1: invokespecial #8                  // Method java/lang/Object."<init>":()V
   4: return        
  }

as in older version of Java implicitly compiler was adding extends Object in byte code as :

public class prashant.CheckObject extends java.lang.Object

so i have two question regarding extends Object:

1) is it not added, because of any performance hit?

2) in which java version it got changed?

java version used to compile this code is 1.6.0_45.

Solution

  • You're printing a disassembly, not the raw bytecode, and the disassembly is designed to be human-readable. An object with no declared superclass necessarily extends Object (as shown by the comment on the constructor), and so listing it is redundant.