java - 方法中列出的赋值是否会导致内存泄漏

Question

我想知道 populateResponse() 中可能的金额重置是否会导致内存泄漏。此类意图用于处理 Web 服务请求。我的理解是，如果对 padAmount() 的调用返回一个新的 BigDecimal，则在 (i) 创建的 BigDecimal 将被视为本地对象实例，并且在方法执行后将超出范围，并将被标记为 GC。这是正确的吗？

public SampleResponse processRequest(SampleRequest request){
        BigDecimal amount = new BigDecimal("12.3000"); // this will pad
        //BigDecimal amount = new BigDecimal("12.35"); // this will not pad, but return passed in amount
        return this.populateResponse(amount);

    }

    public SampleResponse populateResponse(BigDecimal amount){
        BigDecimal finalAmount = new BigDecimal(amount.toString(), new MathContext(21));
        SampleResponse response = new SampleResponse();
        response.setRespAmount(finalAmount.setScale(6, RoundingMode.UP).stripTrailingZeros()); //(i) Setting an amount
        Integer newScale = 2;
        BigDecimal paddedAmount = this.padAmt(newScale, finalAmount);
        response.setRespAmount(paddedAmount); //(ii) Possible reset of amount. Will this cause a memory leak if the paddedAmount has a new memory address
        return response;

    }
    public BigDecimal padAmt(int newScale, BigDecimal amount) {

        String amtWoTrailingZeros = amount.stripTrailingZeros().toPlainString();
        try {
            int decDigitsInAmt = this.getNumberOfDecimalPlaces(amtWoTrailingZeros);
            if(newScale > decDigitsInAmt){
                System.out.println("Pad amount with zeros");
               return new BigDecimal(amtWoTrailingZeros).setScale(newScale);
            }else {
                System.out.println("No Need to pad amount with zeros");
                return amount;
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            System.out.println("Exception caught here: " +e);
            return amount;
        }

    }

    public int getNumberOfDecimalPlaces(String decimalNumber) throws Exception{
        if (decimalNumber == null){
            throw new Exception("decimal number is NULL");
        }
        int index = decimalNumber.indexOf(".");
        return index < 0 ? 0 : decimalNumber.length() - index - 1;
    }

    public static void main (String args[]){
        RequestProcessor rp = new RequestProcessor();
        SampleRequest request = new SampleRequest();
        SampleResponse response = rp.processRequest(request);
        System.out.println("Sample response amount: " +response.getRespAmount().toPlainString());
    }

Answer 1

如果您认为存在内存泄漏，您应该能够通过在某个循环中运行有问题的代码来触发 OutOfMemoryError。但这里似乎没有泄漏!

来自代码中的此注释

Will this cause a memory leak if the paddedAmount has a new memory address?

您似乎对什么是内存泄漏感到非常困惑:当应用程序不再需要的内存仍然被程序使用时，就会发生泄漏。为了发生内存泄漏，需要有一些长期存在的对象(应用程序定义的或语言定义的，如 Class，因此请注意 static 字段!)字节数组、 native 内存等)或存储对象集合且未正确清除的字段。