Android课程---String、StringBuffer 、StringBuilder 的区别(转)
String 字符串常量
package com.hct.test; import java.util.ArrayList;
import java.util.Iterator;
import java.util.List; /**
* @author: chengtai.he
* @created:2009-12-9 上午09:59:57
*/
public class StringBuilderTester {
private static final String base = " base string. ";
private static final int count = 2000000; public static void stringTest() {
long begin, end;
begin = System.currentTimeMillis();
String test = new String(base);
for (int i = 0; i < count/100; i++) {
test = test + " add ";
}
end = System.currentTimeMillis();
System.out.println((end - begin)
+ " millis has elapsed when used String. ");
} public static void stringBufferTest() {
long begin, end;
begin = System.currentTimeMillis();
StringBuffer test = new StringBuffer(base);
for (int i = 0; i < count; i++) {
test = test.append(" add ");
}
end = System.currentTimeMillis();
System.out.println((end - begin)
+ " millis has elapsed when used StringBuffer. ");
} public static void stringBuilderTest() {
long begin, end;
begin = System.currentTimeMillis();
StringBuilder test = new StringBuilder(base);
for (int i = 0; i < count; i++) {
test = test.append(" add ");
}
end = System.currentTimeMillis();
System.out.println((end - begin)
+ " millis has elapsed when used StringBuilder. ");
} public static String appendItemsToStringBuiler(List list) {
StringBuilder b = new StringBuilder(); for (Iterator i = list.iterator(); i.hasNext();) {
b.append(i.next()).append(" ");
} return b.toString();
} public static void addToStringBuilder() {
List list = new ArrayList();
list.add(" I ");
list.add(" play ");
list.add(" Bourgeois ");
list.add(" guitars ");
list.add(" and ");
list.add(" Huber ");
list.add(" banjos "); System.out.println(StringBuilderTester.appendItemsToStirngBuffer(list));
} public static String appendItemsToStirngBuffer(List list) {
StringBuffer b = new StringBuffer(); for (Iterator i = list.iterator(); i.hasNext();) {
b.append(i.next()).append(" ");
} return b.toString();
} public static void addToStringBuffer() {
List list = new ArrayList();
list.add(" I ");
list.add(" play ");
list.add(" Bourgeois ");
list.add(" guitars ");
list.add(" and ");
list.add(" Huber ");
list.add(" banjos "); System.out.println(StringBuilderTester.appendItemsToStirngBuffer(list));
} public static void main(String[] args) {
stringTest();
stringBufferTest();
stringBuilderTest();
addToStringBuffer();
addToStringBuilder();
}
}
运行结果:
5266 millis has elapsed when used String.
375 millis has elapsed when used StringBuffer.
281 millis has elapsed when used StringBuilder.
I play Bourgeois guitars and Huber banjos
I play Bourgeois guitars and Huber banjos
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