（inkfish原创，转载请注明出处：http://blog.csdn.net/inkfish/）
为寻求java代码的性能优化，从网上搜到利用final关键字进行编译时inline优化的方法，但是真的有效吗？实际测试中发现未必，甚至性能影响巨大，最终放弃了使用final优化的想法。
测试环境：Windows XP SP2，JDK 1.6.0_15-b03，Eclipse 3.5 SR1。
package test; public class Test { public static void main(String[] args) { int loop = 10000000;//测试1000万循环 String num = "0"; //----第一遍---- { System.out.print("第一遍：/t"); long start = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { Class1 c1 = new Class1(); c1.setF1(num); c1.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { Class2 c2 = new Class2(); c2.setF1(num); c2.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); Class1 c1 = new Class1(); for (int i = 0; i < loop; i++) { c1.setF1(num); c1.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); Class2 c2 = new Class2(); for (int i = 0; i < loop; i++) { c2.setF1(num); c2.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); } //----第二遍---- { System.out.print("/n第二遍：/t"); long start = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { Class1 c1 = new Class1(); c1.setF1(num); c1.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { Class2 c2 = new Class2(); c2.setF1(num); c2.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); Class1 c1 = new Class1(); for (int i = 0; i < loop; i++) { c1.setF1(num); c1.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); Class2 c2 = new Class2(); for (int i = 0; i < loop; i++) { c2.setF1(num); c2.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); } //----第三遍---- { System.out.print("/n第三遍：/t"); long start = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { Class1 c1 = new Class1(); c1.setF1(num); c1.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { Class2 c2 = new Class2(); c2.setF1(num); c2.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); Class1 c1 = new Class1(); for (int i = 0; i < loop; i++) { c1.setF1(num); c1.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); Class2 c2 = new Class2(); for (int i = 0; i < loop; i++) { c2.setF1(num); c2.getF1(); } System.out.printf("%5dms", (System.currentTimeMillis() - start)); } } } class Class1 { private String f1; public String getF1() { return f1; } public void setF1(String f1) { this.f1 = f1; } } final class Class2 { private String f1; public final String getF1() { return f1; } public final void setF1(String f1) { this.f1 = f1; } }
运行结果：
第一遍： 110ms 1203ms 16ms 156ms 第二遍： 94ms 1203ms 15ms 141ms 第三遍： 94ms 1203ms 15ms 141ms
总结：
1.利用final进行inline优化无效；
2.有时候结果往往出乎多数人预料。
