Java 27 and 26: runnable demos and captured output for every JEP, plus version lanes

Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
2026-09-21 15:08:50 +00:00
commit f59c1de96d
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+java.version = 26.0.2.1
+# VM mode: 64 bits
+# Compressed references (oops): 0-bit shift
+# Compressed class pointers: 0-bit shift and 0x3E000000 base
+# Object alignment: 8 bytes
+#                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
+# Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
+# Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
+# Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16
+
+
+=== java.lang.Object
+java.lang.Object object internals:
+OFF  SZ   TYPE DESCRIPTION               VALUE
+  0   8        (object header: mark)     N/A
+  8   4        (object header: class)    N/A
+ 12   4        (object alignment gap)    
+Instance size: 16 bytes
+Space losses: 0 bytes internal + 4 bytes external = 4 bytes total
+
+
+=== Point { int x; int y; }
+HeaderDemo$Point object internals:
+OFF  SZ   TYPE DESCRIPTION               VALUE
+  0   8        (object header: mark)     N/A
+  8   4        (object header: class)    N/A
+ 12   4    int Point.x                   N/A
+ 16   4    int Point.y                   N/A
+ 20   4        (object alignment gap)    
+Instance size: 24 bytes
+Space losses: 0 bytes internal + 4 bytes external = 4 bytes total
+
+
+=== Order { long id; int quantity; boolean paid; String customer; }
+HeaderDemo$Order object internals:
+OFF  SZ               TYPE DESCRIPTION               VALUE
+  0   8                    (object header: mark)     N/A
+  8   4                    (object header: class)    N/A
+ 12   4                int Order.quantity            N/A
+ 16   8               long Order.id                  N/A
+ 24   1            boolean Order.paid                N/A
+ 25   3                    (alignment/padding gap)   
+ 28   4   java.lang.String Order.customer            N/A
+Instance size: 32 bytes
+Space losses: 3 bytes internal + 0 bytes external = 3 bytes total
+
+
+=== java.lang.Long and java.lang.Integer (boxed values)
+java.lang.Long object internals:
+OFF  SZ   TYPE DESCRIPTION               VALUE
+  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
+  8   4        (object header: class)    0x001a15d0
+ 12   4        (alignment/padding gap)   
+ 16   8   long Long.value                123456789
+Instance size: 24 bytes
+Space losses: 4 bytes internal + 0 bytes external = 4 bytes total
+
+java.lang.Integer object internals:
+OFF  SZ   TYPE DESCRIPTION               VALUE
+  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
+  8   4        (object header: class)    0x0019f570
+ 12   4    int Integer.value             123456
+Instance size: 16 bytes
+Space losses: 0 bytes internal + 0 bytes external = 0 bytes total
+
+
+=== int[3]
+[I object internals:
+OFF  SZ   TYPE DESCRIPTION               VALUE
+  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
+  8   4        (object header: class)    0x00174360
+ 12   4        (array length)            3
+ 16  12    int [I.<elements>             N/A
+ 28   4        (object alignment gap)    
+Instance size: 32 bytes
+Space losses: 0 bytes internal + 4 bytes external = 4 bytes total
+
+
+=== What it adds up to: one million objects
+1,000,000 boxed Integer values in an ArrayList : 20,861,992 bytes
+1,000,000 boxed Long values in an ArrayList    : 28,861,992 bytes
+1,000,000 Point objects in an ArrayList        : 28,861,992 bytes