∟Performance Comparison of String and StringBuffer
This section provides a tutorial example to do a performance comparison of 3 classes: String, StringBuffer, SimpleStringBuffer.
One main reason of using the StringBuffer class instead of the String class is that
StringBuffer performs much better in joining strings together. In order to confirm
this, I wrote the following tutorial example to compare performances of 3 classes:
String, StringBuffer, and SimpleStringBuffer:
/**
* StringBufferTest.java
* Copyright (c) 2003 by Dr. Herong Yang
*/
public class StringBufferTest {
public static void main(String[] args) {
int l = 128;
long t1 = 0;
long t2 = 0;
String s = null;
System.out.println("Initial capacity = "+l);
for (int i=1; i<=3; i++) {
System.out.println("Test: "+i);
t1 = System.currentTimeMillis();
if (i==1) s = stringTest(l);
else if (i==2) s = stringBufferTest(l);
else if (i==3) s = simpleStringBufferTest(l);
t2 = System.currentTimeMillis();
System.out.println(" Final string = "+s);
System.out.println(" Total time = "+(t2-t1));
}
}
public static String stringTest(int l) {
String s = null;
for (int i=0; i<100000; i++) {
String sb = "0";
sb = sb+"01";
sb = sb+"012";
sb = sb+"0123";
sb = sb+"01234";
sb = sb+"012345";
sb = sb+"0123456";
sb = sb+"01234567";
sb = sb+"012345678";
sb = sb+"0123456789";
s = sb;
}
return s;
}
public static String stringBufferTest(int l) {
String s = null;
for (int i=0; i<100000; i++) {
StringBuffer sb = new StringBuffer(l);
sb = sb.append("0");
sb = sb.append("01");
sb = sb.append("012");
sb = sb.append("0123");
sb = sb.append("01234");
sb = sb.append("012345");
sb = sb.append("0123456");
sb = sb.append("01234567");
sb = sb.append("012345678");
sb = sb.append("0123456789");
s = sb.toString();
}
return s;
}
public static String simpleStringBufferTest(int l) {
String s = null;
for (int i=0; i<100000; i++) {
SimpleStringBuffer sb = new SimpleStringBuffer(l);
sb = sb.append("0");
sb = sb.append("01");
sb = sb.append("012");
sb = sb.append("0123");
sb = sb.append("01234");
sb = sb.append("012345");
sb = sb.append("0123456");
sb = sb.append("01234567");
sb = sb.append("012345678");
sb = sb.append("0123456789");
s = sb.toString();
}
return s;
}
}
I compiled and ran the program on J2SDK 1.4.1 with different initial capacities.
Here is the result:
