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javademos/docs/output/10-headers-jdk26.txt
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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