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← Older revision		Revision as of 00:16, 27 March 2026
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	=== 더 할만한것 ===		=== 더 할만한것 ===
	capacity 정보를 제공하는 것이		capacity 정보를 제공하는 것이
	~~~cpp~~ StringBuffer		<code>StringBuffer</code>
	, Vector 밖에 없다. 다른 것들을 볼려면 상속받아서 내부 인자를 봐야 겠다.		, Vector 밖에 없다. 다른 것들을 볼려면 상속받아서 내부 인자를 봐야 겠다.

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	private int totalNumOfData = 1000000;		private int totalNumOfData = 1000000;

	public static void main(String[] args) {		public static void main(String[] args) {
	CapacityTest capacity = new CapacityTest(System.out);		CapacityTest capacity = new CapacityTest(System.out);

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	}		}

imported>Unknown at 05:23, 7 February 2021

2021-02-07T05:23:33Z

New page

재미로 보는 [[Java]] Container Capacity 변화
----

=== 더 할만한것 ===
capacity 정보를 제공하는 것이
~cpp StringBuffer
, Vector 밖에 없다. 다른 것들을 볼려면 상속받아서 내부 인자를 봐야 겠다.

=== 결과 ===
capacity 변화가 있을때 마다만 출력

Show String Buffer capactity by Data I/O in increment
data length: 0 capacity: 16
data length: 17 capacity: 34 <-- 현재 길이의 두배로
data length: 35 capacity: 70
data length: 71 capacity: 142
data length: 143 capacity: 286
data length: 287 capacity: 574
data length: 575 capacity: 1,150
data length: 1,151 capacity: 2,302
data length: 2,303 capacity: 4,606
data length: 4,607 capacity: 9,214
data length: 9,215 capacity: 18,430
data length: 18,431 capacity: 36,862
data length: 36,863 capacity: 73,726
data length: 73,727 capacity: 147,454
data length: 147,455 capacity: 294,910
data length: 294,911 capacity: 589,822
data length: 589,823 capacity: 1,179,646
data length: 1,000,000 capacity: 1,179,646 <-- 마지막 출력은 임의이다.

Show String Buffer capactity by Data I/O in decrement
data length: 1,000,000 capacity: 1,179,646
data length: 0 capacity: 1,179,646 <-- 건드리지 않음

Show Vector capactity by Data I/O in increment
data length: 0 capacity: 10
data length: 11 capacity: 20 <-- 이전 capacity 의 두배로
data length: 21 capacity: 40
data length: 41 capacity: 80
data length: 81 capacity: 160
data length: 161 capacity: 320
data length: 321 capacity: 640
data length: 641 capacity: 1,280
data length: 1,281 capacity: 2,560
data length: 2,561 capacity: 5,120
data length: 5,121 capacity: 10,240
data length: 10,241 capacity: 20,480
data length: 20,481 capacity: 40,960
data length: 40,961 capacity: 81,920
data length: 81,921 capacity: 163,840
data length: 163,841 capacity: 327,680
data length: 327,681 capacity: 655,360
data length: 655,361 capacity: 1,310,720
data length: 1,000,000 capacity: 1,310,720 <-- 마지막 출력은 임의이다.

Show String Buffer capactity by Data I/O in decrement
data length: 1,000,000 capacity: 1,310,720
data length: 0 capacity: 1,310,720 <-- 건드리지 않음

=== 소스 ===
이런;; 간단한 소스가 늘어나 버린것 처럼 보인다.
import java.io.PrintStream;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.Vector;

public class CapacityTest {
private static final int NUMBER_LIMIT_LEN = 10;
private PrintStream out;
private PrintWriter k;
private int totalNumOfData = 1000000;

public static void main(String[] args) {
CapacityTest capacity = new CapacityTest(System.out);

capacity.testStringBuffer();
capacity.testVector();

}
public CapacityTest(PrintStream anOut) {
out = anOut;
if (out == null)
throw new NullPointerException("out is null");
}
public void testStringBuffer() {
StringBuffer stringBuffer = new StringBuffer();
showStringBufferIncrease(stringBuffer);
showStringBufferDecrease(stringBuffer);
}
public void testVector() {
Vector vector = new Vector();
showVectorIncrease(vector);
showVectorDecrease(vector);
}

private void printTitle(String aContainerKind, String aSituation) {
out.println();
out.println(
"Show "
+ aContainerKind
+ " capactity by Data I/O in "
+ aSituation);
}
private void printContainerState(int aSize, int aCapacity) {
DecimalFormat df = new DecimalFormat("###,###,###");

String size = df.format(aSize);
String capacity = df.format(aCapacity);

size = getShowedString(size, NUMBER_LIMIT_LEN);
capacity = getShowedString(capacity, NUMBER_LIMIT_LEN);

out.println("data length:" + size + "\tcapacity:" + capacity);
}
private String getShowedString(String aSrc, int aLimit) {
int insufficientLen = aLimit - aSrc.length();
StringBuffer showedString = new StringBuffer(aLimit);
for (int i = 0; i < insufficientLen; i++)
showedString.append(" ");
showedString.append(aSrc);
return showedString.toString();
}

public void showStringBufferIncrease(StringBuffer stringBuffer) {
printTitle("String Buffer", "increment");
printContainerState(stringBuffer.length(), stringBuffer.capacity());

for (int length = 0; length < totalNumOfData; length++) {
int oldCapacity = stringBuffer.capacity();
stringBuffer.append((char) ('a' + length % 26));

if (oldCapacity != stringBuffer.capacity())
printContainerState(
stringBuffer.length(),
stringBuffer.capacity());
}
printContainerState(stringBuffer.length(), stringBuffer.capacity());
}
public void showStringBufferDecrease(StringBuffer stringBuffer) {

printTitle("String Buffer", "decrement");
printContainerState(stringBuffer.length(), stringBuffer.capacity());

for (int counter = stringBuffer.length(); counter > 0; counter--) {
int oldCapacity = stringBuffer.capacity();
stringBuffer.delete(
stringBuffer.length() - 1,
stringBuffer.length());

if (oldCapacity != stringBuffer.capacity())
printContainerState(
stringBuffer.length(),
stringBuffer.capacity());
}
printContainerState(stringBuffer.length(), stringBuffer.capacity());
}
public void showVectorIncrease(Vector aVector) {
printTitle("Vector", "increment");
printContainerState(aVector.size(), aVector.capacity());

for (int size = 0; size < totalNumOfData; size++) {
int oldCapacity = aVector.capacity();
aVector.add("This is Gabage Data");

if (oldCapacity != aVector.capacity())
printContainerState(aVector.size(), aVector.capacity());
}
printContainerState(aVector.size(), aVector.capacity());
}
public void showVectorDecrease(Vector aVector) {
printTitle("String Buffer", "decrement");
printContainerState(aVector.size(), aVector.capacity());

for (int counter = aVector.size(); counter > 0; counter--) {
int oldCapacity = aVector.capacity();
aVector.remove(aVector.size() - 1);

if (oldCapacity != aVector.capacity())
printContainerState(aVector.size(), aVector.capacity());
}
printContainerState(aVector.size(), aVector.capacity());
}

}

Java/CapacityIsChangedByDataIO - Revision history

Maintenance script: Repair batch-0002 pages from live compare

imported>Unknown at 05:23, 7 February 2021