在具有许多if语句的for循环中继续使用时，是否可以获得性能? [英] Is performance gained when using continue in a for-loop with many if-statements?

问题描述

我在Java程序中有一个for循环，该循环遍历一组映射.

I have a for loop in a java program which iterates through a set of maps.

在循环中，我有大约10种不同的if语句，用于检查每个映射中每个键的名称.

Inside the loop I have around 10 different if-statements which checks the name of each key inside the each map.

示例:

for (<String, Object> map : object.entrySet()) {
  if (map.getKey().equals.("something") {
    do_something;
    continue;   
  }
  if (map.getKey().equals.("something_else") {
    do_something_else;
    continue;
  }
  if ...
}

添加像这样的连续语句时，我是否可以获得任何性能?

Do I gain any performance when adding continue-statements like this?

当我在IDE中逐步执行代码而没有这些continue语句时，即使第一个匹配，也会测试每个if语句.

When I step through my code in my IDE and NOT have these continue statements, each if-statement will be tested even if the first one matches.

如果我像这样，并且第一个if匹配，则for循环将跳过接下来的9个if语句，并继续下一个对象. 也许编译后的代码会对它有所不同，而添加的continue语句实际上会使循环变慢了?

If I have them like this and the first if matches, the for loop will skip the next 9 if-statements and continue with the next object. Maybe the compiled code will treat it differently and the added continue-statements actually makes the loop slower?

推荐答案

而不是一直使用continue，只需执行一次getKey()并使用else if:

Instead of using continue all the time, do the getKey() just once and use else if:

for (Map.Entry<String, Object> entry : map.entrySet()) {
    String key = entry.getKey();
    if (key.equals("something")) {
        // ...
    } else if (key.equals("something else")) {
        // ...
    }
}

或使用switch语句:

for (Map.Entry<String, Object> entry : map.entrySet()) {
    switch (entry.getKey()) {
        case "something":
            // ...
            break;

        case "something else":
            // ...
            break;
}

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