자바 최적화를 위한 5가지

1. 불필요한 캐스팅 피한다.

class MyCastingClass {
	public Object myMethod() {
		String myString = "Some data";
		Object myObj = (Object) myString;
		return myObj;
	}
}









class MyCastingClass {
	public Object myMethod() {
		return "Some data";
	}
}


 

2. 일반적인 하위 표현식 제거

int someNumber = (someValue * number1 / number2) + otherValue;
int someNumber2 = (someValue * number1 / number2) +

final int constantCalculation = (someValue * number1 / number2);
int someNumber = (constantCalculation) + otherValue;
int someNumber2 = (constantCalculation) + otherValue2;
 

3. Use StringBuffer (or StringBuilder) instead of string for non-constant strings

class MyStringClass {
	public void myMethod() {
		String myString = "Some data";

		for (int i = 0; i < 20; i++) {
			myString += getMoreChars();
		}
	}
}	







class MyCastingClass {
	public Object myMethod() {
		String myString = "Some data";
		StringBuffer myBuffer = new StringBuffer();

		for (int i = 0; i < 20; i++) {
			myBuffer.append(getMoreChars());
		}
		myString = myBuffer.toString();
	}
}


 

4. Use Short Circuit Boolean Operators

class MyShortCircuitClass {
	public void myMethod() {
		if (someValue.equals("true") | someValue.equals("false")) {
			System.out.println("valid boolean");
		}
	}
}





class MyCastingClass {
	public void myMethod() {
		if ("true".equals(someValue) || "false".equals(someValue)) {
			System.out.println("valid boolean");
		}
	}
}

Here’s a table describing four of Java’s boolean operators:

	Meaning	Short circuit?
&&	and	yes
&	and	no
||	or	yes
|	or	no

5.  Use length() instead of equals() to find the length of a string

 class MyStringClass {

	public boolean myTestMethod() {
		return myString.equals("");
	}
}

class MyCastingClass {
	public void myMethod() {
		public boolean myTestMethod() {
			// which really does myString.length() == 0 behind the schenes
			return myString.isEmpty();
		}
	}
}