java自动装箱、自动拆箱和正常情况性能比较

自动装箱和自动拆箱是java5.0版本引入的，能自动将基本类型转换为对应的基本类型包装对象，那么我们比较一下他们的性能情况。
package com.wmmad.test;
import junit.framework.TestCase;
/**
* @author madding.lip
*
* <pre>
* class: compare the autoboxing and unboxing and normal's performance
* </pre>
*
*/
@SuppressWarnings("unused")
public class BoxTest extends TestCase {
public static void main(String[] args) {
testAutoboxing();
testUnboxing();
testChangeToObject();
testChangeToData();
testNormal();
testNormal1();
}
public static void testAutoboxing() {
long start = System.currentTimeMillis();
Integer result = 0;
for (int i = 0; i < 1000000000; i++) {
result = i; // autoboxing
}
long end = System.currentTimeMillis();
System.out.println("autoboxing use time is： " + (end - start) + "ms");
}
public static void testUnboxing() {
int result = 0;
long start = System.currentTimeMillis();
for (Integer i = 0; i < 1000000000; i++) {
result = i;
}
long end = System.currentTimeMillis();
System.out.println("unboxing use time is： " + (end - start) + "ms");
}

public static void testChangeToObject() {
Integer result = 0;
long start = System.currentTimeMillis();
for(int i = 0; i < 1000000000; i++) {
result = (Integer)i;
}
long end = System.currentTimeMillis();
System.out.println("change to object use time is: " + (end - start) + "ms");
}

public static void testChangeToData() {
int result = 0;
long start = System.currentTimeMillis();
for(Integer i = 0; i < 1000000000; i++) {
result = i.intValue();
}
long end = System.currentTimeMillis();
System.out.println("change to data use time is: " + (end - start) + "ms");
}
public static void testNormal() {
int result = 0;
long start = System.currentTimeMillis();
for (int i = 0; i