Java - By default what debug information is added in class file?

Java Tools & Commands 

By default javac includes only line number and source file information in the compiled class file which is equivalent to
-g:source,lines.
Also check out what is -g option?.

Let's confirm what debug info is included in the class file with an example.

public class Test {

  public void execute(int myNumber, String message) {
  }
}

D:\java-class-default-debug-info>javac Test.java

Let's use javap command with -l option (-l option prints line and local variable tables).

D:\java-class-default-debug-info>javap -l Test
Compiled from "Test.java"
public class Test {
  public Test();
    LineNumberTable:
      line 2: 0

  public void execute(int, java.lang.String);
    LineNumberTable:
      line 5: 0
}

No local variable names are included.

Let's compile with vars and other information included:

D:\java-class-default-debug-info>javac -g:vars,source,lines Test.java

D:\java-class-default-debug-info>javap -l Test
Compiled from "Test.java"
public class Test {
  public Test();
    LineNumberTable:
      line 2: 0
    LocalVariableTable:
      Start  Length  Slot  Name   Signature
          0       5     0  this   LTest;

  public void execute(int, java.lang.String);
    LineNumberTable:
      line 5: 0
    LocalVariableTable:
      Start  Length  Slot  Name   Signature
          0       1     0  this   LTest;
          0       1     1 myNumber   I
          0       1     2 message   Ljava/lang/String;
}

As seen this time local variables names are also included.