Java中boolean到底占几个字节

看到Java的基本类型，突然想到boolean 占几个字节？第一反应：1byte

不确定，查之。在这个帖子上讨论过：

java中的 boolean 在内存中占多少字节？

但众说纷纭，没有一个令人信服的答案，唯一的线索是：boolean的大小JVM规范并没有指定。

最后在stackoverflow上找到答案（What is the size of boolean variable in Java）：

It depends on Java virtual machine

可以用下面的代码粗略得出:

class LotsOfBooleans
{
boolean a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, aa, ab, ac, ad, ae, af;
boolean b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf;
boolean c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, ca, cb, cc, cd, ce, cf;
boolean d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, da, db, dc, dd, de, df;
boolean e0, e1, e2, e3, e4, e5, e6, e7, e8, e9, ea, eb, ec, ed, ee, ef;
}

class LotsOfInts
{
int a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, aa, ab, ac, ad, ae, af;
int b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf;
int c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, ca, cb, cc, cd, ce, cf;
int d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, da, db, dc, dd, de, df;
int e0, e1, e2, e3, e4, e5, e6, e7, e8, e9, ea, eb, ec, ed, ee, ef;
}

public class Test
{
private static final int SIZE = 100000;

public static void main(String[] args) throws Exception
{
LotsOfBooleans[] first = new LotsOfBooleans[SIZE];
LotsOfInts[] second = new LotsOfInts[SIZE];

System.gc();
long startMem = getMemory();

for (int i=0; i < SIZE; i++)
{
first[i] = new LotsOfBooleans();
}

System.gc();
long endMem = getMemory();

System.out.println ("Size for LotsOfBooleans: " + (endMem-startMem));
System.out.println ("Average size: " + ((endMem-startMem) / ((double)SIZE)));

System.gc();
startMem = getMemory();
for (int i=0; i < SIZE; i++)
{
second[i] = new LotsOfInts();
}
System.gc();
endMem = getMemory();

System.out.println ("Size for LotsOfInts: " + (endMem-startMem));
System.out.println ("Average size: " + ((endMem-startMem) / ((double)SIZE)));

// Make sure nothing gets collected
long total = 0;
for (int i=0; i < SIZE; i++)
{
total += (first[i].a0 ? 1 : 0) + second[i].a0;
}
System.out.println(total);
}

private static long getMemory()
{
Runtime runtime = Runtime.getRuntime();
return runtime.totalMemory() - runtime.freeMemory();
}
}



我的机器运行结果：
Size for LotsOfBooleans: 8784984

Average size: 87.84984

Size for LotsOfInts: 32800000

Average size: 328.0

在我使用的JVM上boolean是1byte