Java 字符串参数化 - 间接 toString 方法的性能损失 [英] Java String Parameterization - Performace loss on indirect toString methods

问题描述

我有一个像这样的 method:

private String getOrderListAsString() {
    StringBuilder str = new StringBuilder();
    str.append("Sell list:");
    for (Order o : sellOrderList) {
        str.append("\nSale: ").append(o);
    }
    str.append("Buy list:");
    for (Order o : buyOrderList) {
        str.append("\nBuy:  ").append(o);
    }
    return str.toString();
}

使用日志参数化调用它，如下所示:我们正在使用 java.util.logging 作为记录器.

It's called with logging parameterization like so: We're using java.util.logging as a logger.

logger.log(Level.INFO, "{0}", getOrderListAsString());

问题是，即使记录器级别为 Level.OFF，字符串连接仍在进行中.
为了解决这个问题，我们在方法的开头添加了一个 if 语句:

The problem is that the string concatination is still being done even if the logger level is Level.OFF.
To get around this we've added an if statement at the start of the method:

// Declaration:
boolean shouldLog = DebugWriter.getInstance().getLogger().getLevel() != Level.OFF;
// Usage in function:
if(!shouldLog) return null;

但感觉这可以以更聪明的方式完成.提前致谢！

But it feels like this could be done in a more clever way. Thanks in advance!

推荐答案

如果您使用的是 Java 8+，那么 java.util.Logger 会重载 log 采用供应商的方法

If you are using Java 8+, then java.util.Logger has an overload of the log method that takes a Supplier

public void log(Level level,
            Supplier<String> msgSupplier)

现在，您可以制作从供应商处生成的字符串

Now, you can make the string generated from a supplier like

logger.log(Level.INFO, () -> getOrderListAsString());

或者，使用方法引用

logger.log(Level.INFO, this::getOrderListAsString);

Javadoc

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