如果可以的话，我可以在不使用java中的Wrapper类的情况下求和两个String值吗？

Question

String result = "";
try{
 int value = Integer.parseInt(a)+Integer.parseInt(b);
 result = ""+value;
}catch(NumberFormatException ex){
 //either a or b is not a number
 result = "Invalid input";
}
MyStringSum.show(null,a+b);

I am using Wrapper Class but i want to sum two String values without using
Wrapper Class , can i do this?

Answer 1

You should not worry about the efficiency of your implementation, because it is not using any wrapper objects.

java.lang.Integer plays several roles:

1. It holds several important constants, such as MIN_VALUE and MAX_VALUE ,
2. It serves as a helper class for working with primitive int s by providing class methods for parsing and manipulating them, and
3. Its instances serve as Object wrappers for primitive int s, and providing instance methods for it.

Because you use only parse(...) , which is a class method , your code uses the class in its capacity #2, ignoring the #1 and #3. In other words, you are not using Integer in its "wrapper for int " capacity.

Answer 2

Try exp4j . Example(from the link):

Expression e = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)")
        .variables("x", "y")
        .build()
        .setVariable("x", 2.3)
        .setVariable("y", 3.14);
double result = e.evaluate();

Another option is Javaluator . See the link for example.

And there's EvalX . See below example(from the link):

Expression expression = new Expression("1+1/3");
result = expression.eval():
expression.setPrecision(2);
result = expression.eval():

I hope this helps!