java效能調優(使用局部變數)

標籤：java   效能調優   

/*
 * Created on Jan 29, 2015
 *
 *  */
package com.zcd.test;

import java.sql.Timestamp;

public class Test {

 private int x;
 private static int staticX;

 public void stackAccess(int val) {
  int j = 0;
  for (int i = 0; i < val; i++) {
   j += 1;
  }
 }

 public void instanceAccess(int val) {
  for (int i = 0; i < val; i++) {
   x += 1;
  }
 }

 public void staticAccess(int val) {
  int tempX=staticX;
  for (int i = 0; i < val; i++) {
   tempX += 1;
  }
 }

 public static void main(String[] args) {
  System.out.println(new Timestamp(System.currentTimeMillis()));
  Test test=new Test();
  long t1Start=System.currentTimeMillis();
  test.stackAccess(1000000000);
  long t1End=System.currentTimeMillis();
  System.out.println("Time1="+(t1End-t1Start));
  long t2Start=System.currentTimeMillis();
  test.instanceAccess(1000000000);
  long t2End=System.currentTimeMillis();
  System.out.println("Time2="+(t2End-t2Start));
  long t3Start=System.currentTimeMillis();
  test.staticAccess(1000000000);
  long t3End=System.currentTimeMillis();
  System.out.println("Time3="+(t3End-t3Start));
 }
}

==========================================================================

調優後代碼：

/*
 * Created on Jan 29, 2015
 *
 * Copyright 2006 ATPCO Confidential and Proprietary. All Rights Reserved.
 */
package com.zcd.test;

import java.sql.Timestamp;

public class Test {

 private int x;
 private static int staticX;

 public void stackAccess(int val) {
  int j = 0;
  for (int i = 0; i < val; i++) {
   j += 1;
  }
 }

 public void instanceAccess(int val) {
  int tempX=x;
  for (int i = 0; i < val; i++) {
   tempX += 1;
  }
 }

 public void staticAccess(int val) {
  int tempX=staticX;
  for (int i = 0; i < val; i++) {
   tempX += 1;
  }
 }

 public static void main(String[] args) {
  System.out.println(new Timestamp(System.currentTimeMillis()));
  Test test=new Test();
  long t1Start=System.currentTimeMillis();
  test.stackAccess(1000000000);
  long t1End=System.currentTimeMillis();
  System.out.println("Time1="+(t1End-t1Start));
  long t2Start=System.currentTimeMillis();
  test.instanceAccess(1000000000);
  long t2End=System.currentTimeMillis();
  System.out.println("Time2="+(t2End-t2Start));
  long t3Start=System.currentTimeMillis();
  test.staticAccess(1000000000);
  long t3End=System.currentTimeMillis();
  System.out.println("Time3="+(t3End-t3Start));
 }
}

java效能調優(使用局部變數)