Quoting the following from Algorithms 4th edition
"For example, if you have 1GB of memory on your computer (1 billion bytes), you cannot fit more than about 32 million int values or 16 million double values in memory at one time."
int - 4 bytes
32 million x 4 = 128 million bytes
Help me understand, why we can't fit 32 million int values, the above 128 million bytes is about 1/10 of the overall memory consumption of 1GB or 1 billion bytes.
That depends on how you organize your data. In Java, every object has an overhead, this is JVM dependent, but typically 8 or 16 bytes. So if you wrap every int value into an object (like Integer), then you may exceed 1GB. But, if you allocate it as an int[] array, then it should fit into 1GB easily.
And, this is not strictly related to the question, but reflecting to @Anony-Mousse's comment, there are JVMs for microcontrollers, and I am pretty sure that object size is below 8 bytes in those JVMs (though I didn't find exact data).