Por que o método getBytes de String nativo é mais lento que o getBytesFast implementado customizado?
Ao executar o seguinte trecho de código, a execução do método nativo do Java StringgetBytes () parece serMais devagar do que o costumegetBytesFast () implementação. Você pode usar oArrays.equals(str.getBytes(), getBytesFast(str))
para verificar se ambas as matrizes de bytes são iguais.
A implementação de getBytesFast é uma versão modificada da implementação incluída neste artigo de dicas de programação (1997):http://java.sun.com/developer/technicalArticles/Programming/Performance/
Estou procurando uma resposta bem documentada sobre por que a implementação nativa é mais lenta que a implementação personalizada.
package com.test;
public class Performance {
public static void main(String args[]) {
final String str = "This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! 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This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test! This is a performance test!";
long startTime_1 = System.nanoTime();
str.getBytes();
System.out.println(System.nanoTime() - startTime_1);
long startTime_2 = System.nanoTime();
getBytesFast(str);
System.out.println(System.nanoTime() - startTime_2);
}
private static byte[] getBytesFast(String str) {
final char buffer[] = new char[str.length()];
final int length = str.length();
str.getChars(0, length, buffer, 0);
final byte b[] = new byte[length];
for (int j = 0; j < length; j++)
b[j] = (byte) buffer[j];
return b;
}
}
EDITADO:
Resultados de benchmark Caliper
obrigado