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Option 1:
String newStr = someStr + 3 + "]";
Option 2:
String newStr = someStr + "3" + "]";
Which option is better with regards to performance, memory and general practice? What are some recommended tools/ways I can use to measure memory usage of my code and its performance (besides measuring the start time and the end time and calculate the difference)
687
To concatenate a string to an int value, use the concatenation operator. Here is our int. int val = 3; Now, to concatenate a string, you need to declare a string and use the + operator.
Using + Operator The + operator is one of the easiest ways to concatenate two strings in Java that is used by the vast majority of Java developers. We can also use it to concatenate the string with other data types such as an integer, long, etc.
You can use the String concatenation operator + to concatenate integers to a string in a clear and concise manner. Note that the compiler implicitly constructs an intermediate StringBuilder object, append the integers, and then call the toString() method.
Syntax: public String concat(String another)
The first will become:
StringBuilder sb = new StringBuilder (String.valueOf (someStr));
sb.append (3);
sb.append ("]");
String newStr = sb.toString ();
the second will become:
StringBuilder sb = new StringBuilder (String.valueOf (someStr));
sb.append ("3");
sb.append ("]");
String newStr = sb.toString ();
Here is disassembly:
public String foo (String someStr)
{
String newStr = someStr + 3 + "]";
return newStr;
}
public String bar (String someStr)
{
String newStr = someStr + "3" + "]";
return newStr;
}
public java.lang.String foo(java.lang.String);
Code:
0: new #16 // class java/lang/StringBuilder
3: dup
4: aload_1
5: invokestatic #18 // Method java/lang/String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
8: invokespecial #24 // Method java/lang/StringBuilder."<init>":(Ljava/lang/String;)V
11: iconst_3
12: invokevirtual #27 // Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
15: ldc #31 // String ]
17: invokevirtual #33 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
20: invokevirtual #36 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
23: astore_2
24: aload_2
25: areturn
public java.lang.String bar(java.lang.String);
Code:
0: new #16 // class java/lang/StringBuilder
3: dup
4: aload_1
5: invokestatic #18 // Method java/lang/String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
8: invokespecial #24 // Method java/lang/StringBuilder."<init>":(Ljava/lang/String;)V
11: ldc #44 // String 3
13: invokevirtual #33 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
16: ldc #31 // String ]
18: invokevirtual #33 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
21: invokevirtual #36 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
24: astore_2
25: aload_2
26: areturn
There won't be any noticeable difference between both. Use what you find the most logical and readable. I would use
String newStr = someStr + "3]";
I would recommend Jprofiler as a great java application profiling tool that helped me find lots of memory problems.
I don't think option 1 and 2 have a big difference in terms of memory usage, especially if it is for a desktop application.
20
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