Green Java

Transcript

1. Volcamp 2023 ☕
2. Volcamp 2023
12. Electricité 41% Transport 24% Industrie et construction 19% Autres 16%
34. 80 60 40 20 0 Normalized global results for energy
55. RAPL (Running Average Power Limit) JRAPL
56. ??????????????? ?
60. 1 byte model
63. ClassLayout.parseClass(TestJOL.class).toPrintable() ClassLayout.parseInstance(new TestJOL()).toPrintable() GraphLayout.parseInstance(new TestJOL()).toPrintable(
65. String var1 = getValue(); return var1;
66. String var1 = getValue(); return var1; return getValue(); Do not unnecessarily assign values to variables. It increases the use of RAM memory. A noter que la JVM optimise de toute façon ce code lors de la compilation de la version sale à la version green.
67. libérer les ressources => try with ressources primitive vs Object => ex Long vs long A venir: les value objects
68. public String concatenateStrings(String[] strings) { String result = ""; for (String string : strings) { result += string; } return result; }
69. public String concatenateStrings(String[] strings) { String result = ""; for (String string : strings) { result += string; } return result; } public String concatenateStrings(String[] strings) { StringBuilder result = new StringBuilder(); for (String string : strings) { result.append(string); } return result.toString(); } Don't concatenate Strings in loop. Use StringBuilder instead. Strings are immutable so each time you concatenate a String, a new String is created. This is a waste of memory and CPU.
70. public voidfoo() { for (int i = 0; i < getMyValue(); i++) { System.out.println(i); } }
71. public voidfoo() { for (int i = 0; i < getMyValue(); i++) { System.out.println(i); } } public voidfoo() { int myValue =getMyValue(); for (int i = 0; i < myValue; i++) { System.out.println(i); } } Do not call a function when declaring a for-type loop in order to avoid function calls each iterations. It saves CPU cycles.
72. Stream .iterate(0, i -> i++) .limit(100) .reduce(0, Integer::sum) IntStream .iterate(0, i -> i++) .limit(100) .sum()
73. Stream .iterate(0, i -> i++) .limit(100) .reduce(0, Integer::sum) IntStream .iterate(0, i -> i++) .limit(100) .sum()
74. Eviter d’utiliser des Wrappers sur les primitifs Utiliser la bonne Collection pour son besoin JDBC < Spring Data JPA native queries < JPQL* Switch plutôt que if/else Threads virtuels *Tests faits sur une base oracle