Ethanlm commented on a change in pull request #3368:
URL: https://github.com/apache/storm/pull/3368#discussion_r548240226
##########
File path: storm-client/src/jvm/org/apache/storm/utils/Utils.java
##########
@@ -1039,7 +1039,7 @@ public static Double
parseJvmHeapMemByChildOpts(List<String> options, Double def
}
Matcher m = optsPattern.matcher(option);
while (m.find()) {
- int value = Integer.parseInt(m.group(1));
+ long value = Long.parseLong(m.group(1));
Review comment:
https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.7
> The left-hand operand of a binary operator appears to be fully evaluated
before any part of the right-hand operand is evaluated.
> The Java programming language guarantees that every operand of an operator
(except the conditional operators &&, ||, and ? :) appears to be fully
evaluated before any part of the operation itself is performed.
So I would look at `value * unit / 1024.0 / 1024.0; ` as
```
int tmp = value * unit;
double tmp1 = tmp / 1024.0;
double tmp2 = tmp1 / 1024.0;
```
And the Widening Primitive Conversion happens at each operation. Looking at
the byte code of this short example
java:
```
public static void main(String[] args) {
int value = 2;
int unit = 1024 * 1024 * 1024;
double result = value * unit / 1024.0 / 1024.0 ;
System.out.println(result);
}
```
bytecode:
```
public static void main(java.lang.String[]);
Code:
0: iconst_2
1: istore_1
2: ldc #2 // int 1073741824
4: istore_2
5: iload_1
6: iload_2
7: imul
8: i2d
9: ldc2_w #3 // double 1024.0d
12: ddiv
13: ldc2_w #3 // double 1024.0d
16: ddiv
17: dstore_3
18: getstatic #5 // Field
java/lang/System.out:Ljava/io/PrintStream;
21: dload_3
22: invokevirtual #6 // Method
java/io/PrintStream.println:(D)V
25: return
}
```
It first calculate `value * unit` based on integer. Then on line8, `i2d` is
invoked to convert integer to double.
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