Java Best Practices – String performance and Exact String MatchingDirk Ludwig
We have written the JMH class to benchmark all these methods (in Java 21) as follows: importjava.util.concurrent.ThreadLocalRandom;importjava.util.concurrent.TimeUnit;importorg.openjdk.jmh.annotations.Benchmark;importorg.openjdk.jmh.annotations.BenchmarkMode;importorg.openjdk.jmh.annotations.Mode;i...
在主流高性能的JVM上(HotSpot VM系、IBM J9 VM系、JRockit系等等),可以认为System.arraycopy()在拷贝数组时是可靠高效的——如果发现不够高效的情况,请报告performance bug,肯定很快就会得到改进。 java.lang.System.arraycopy()方法在Java代码里声明为一个native方法。所以最naïve的实现方式就是通过JNI调用JVM里的...
英文原文链接:http://java-performance.info/string-intern-in-java-6-7-8/ 本文将描述JDK6中String.intern()是如何实现的,以及在JDK7和JDK8中对字符串池化技术做了哪些改变。 String池化介绍 String池化就是把一些值相同,但是标识符不同的字符串用一个共享的String对象来表示,而不是用多个String对象。举个栗...
The benefits of theparseLong(String)method to convert a String to alongorintin Java instead of thevalueOf(String)or the deprecated contructor method include: TheLong.parseLong()method returns a long primitive, not a wrapper. The Long.parseLong()method uses the Long class, which is semantically...
* interned. String literals are defined in section 3.10.5 of the * The Java Language Specification. *@returna string that has the same contents as this string, but is guaranteed to be from a pool of unique strings. */publicnativeString...
在java中,大家肯定都会遇到int类型转String类型的情形,知其然知其所以然。总结加分析一下,int类型转String类型有下面几种方式: a+”“ String.valueOf(a) Integer.toString(a) 以上三种方法在实际使用过程中都是没有问题的,可是效率上还是有些许区别的,所以写个小程序来对照一下他们的效率: ...
在java中,大家肯定都会遇到int类型转String类型的情形,知其然知其所以然。总结加分析一下,int类型转String类型有下面几种方式: 1.a+”“2.String.valueOf(a)3.Integer.toString(a) 1. 2. 3. 以上三种方法在实际使用过程中都是没有问题的,可是效率上还是有些许区别的,所以写个小程序来对照一下他们的效率:...
@OutputTimeUnit(TimeUnit.NANOSECONDS)publicclassStringContainsPerformanceTest{@State(Scope.Thread)publicstaticclassMyState{privateStringtext="If you want to be smart; read. If you want to be really smart; read a lot.";Patternpattern=Pattern.compile("read");}@BenchmarkpublicintindexOf(MyStatestate...
int index = 0; while ((index = string.indexOf(".", index)) != -1) { System.out.println (string.substring(index, string.length())); } } } 1. 2. 3. 4. 5. 6. 7. 8. 参考资料: Graig Larman, Rhett Guthrie: "Java 2Performance and Idiom Guide" ...