Java Object Size

public class SimpleClass {
  public int x;
}
For 32bit Java, the size of the object is 16 bytes.
For 64bit Java, size is 24 bytes

public class SimpleClass {
  public int x;
  public int y;
}

public class SimpleClass {
  public int x;
  public int y;
  public int z;
}

______32-bit 64-bit
Object 8 16
Integer 16 24
Long 16 24
Float 16 24
Double 16 24
String 40 64
Date 24 32
Calendar 432 544
byte[0] 16 24
byte[32] 48 56
byte[128][0] 2576 4120
ArrayList(1) 56 96
ArrayList(2) 80 128