Notice
I wrote this article and was originally published on Qiita on 14 September 2021.
There are 4 internal indicators (capacity, limit, position, remaining) in Buffer classes, example below shows the change of these indicators.
import java.nio.Buffer;
import java.nio.ByteBuffer;
public class BufferTest {
public static void main(String[] args) {
ByteBuffer buf = ByteBuffer.allocate(8);
System.out.println("[new buf]");
printBufferInfo(buf);
buf.put((byte) 1).put((byte) 2).put((byte) 3);
System.out.println("[put 3 elements]");
printBufferInfo(buf);
for (int i = 0; i < buf.position(); i++)
System.out.println(buf.get(i));
System.out.println("[get 3 elements by index]");
printBufferInfo(buf);
buf.flip();
System.out.println("[flip]");
printBufferInfo(buf);
for (int i = 0; i < 2; i++)
System.out.println(buf.get());
System.out.println("[get 2 elements]");
printBufferInfo(buf);
buf.compact();
System.out.println("[compat]");
printBufferInfo(buf);
buf.put((byte) 4);
System.out.println("[put 1 element]");
printBufferInfo(buf);
buf.clear();
System.out.println("[clear]");
printBufferInfo(buf);
}
public static void printBufferInfo(Buffer buf) {
System.out.println("Capacity: " + buf.capacity());
System.out.println("Limit: " + buf.limit());
System.out.println("Position: " + buf.position());
System.out.println("Remaining: " + buf.remaining());
}
}
The output is
[new buf]
Capacity: 8
Limit: 8
Position: 0
Remaining: 8
[put 3 elements]
Capacity: 8
Limit: 8
Position: 3
Remaining: 5
1
2
3
[get 3 elements by index]
Capacity: 8
Limit: 8
Position: 3
Remaining: 5
[flip]
Capacity: 8
Limit: 3
Position: 0
Remaining: 3
1
2
[get 2 elements]
Capacity: 8
Limit: 3
Position: 2
Remaining: 1
[compat]
Capacity: 8
Limit: 8
Position: 1
Remaining: 7
[put 1 element]
Capacity: 8
Limit: 8
Position: 2
Remaining: 6
[clear]
Capacity: 8
Limit: 8
Position: 0
Remaining: 8
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