April 2025
Intermediate to advanced
450 pages
14h 9m
Portuguese (Portugal, Brazil)
Content preview from Desempenho do Java, 2ª Edição
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Capítulo 12. Dicas da API do Java SE
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Este capítulo cobre áreas da API do Java SE que têm peculiaridades de implementação que afetam seu desempenho. Muitos desses detalhes de implementação existem em todo o JDK; essas são as áreas em que sempre descubro problemas de desempenho (mesmo em meu próprio código). Este capítulo inclui detalhes sobre a melhor maneira de lidar com strings (e especialmente strings duplicadas); maneiras de armazenar E/S adequadamente em buffer; carregamento de classes e maneiras de melhorar o startup de aplicativos que usam muitas classes; uso adequado de coleções; e recursos do JDK 8 como lambdas e streams.
Cordas
As cadeias de caracteres são (sem surpresa) o objeto Java mais comum. Nesta secção, veremos uma variedade de formas de lidar com toda a memória consumida pelos objectos string; estas técnicas podem muitas vezes reduzir significativamente a quantidade de heap que o teu programa requer. Também abordaremos um novo recurso do JDK 11 de strings envolvendo concatenação.
Cordas compactas
Em Java 8, todas as cadeias de caracteres são codificadas como matrizes de caracteres de 16 bits, independentemente da codificação da cadeia. Isto é um desperdício: a maioria das localidades ocidentais pode codificar cadeias de caracteres em arrays de bytes de 8 bits, e mesmo numa localidade que requer 16 bits para todos os caracteres, cadeias de caracteres ...
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