Не понимаю какой именно формат хочет валидатор
package com.javarush.task.task19.task1914;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
/*
Решаем пример
*/
public class Solution {
public static TestString testString = new TestString();
private static String eval(String expr) {
String res = expr;
expr = expr.trim().replace(" ", "").replace("=", "");
if (expr.contains("+")) {
String[] nums = expr.split("\\+");
int a = Integer.valueOf(nums[0]).intValue();
int b = Integer.valueOf(nums[1]).intValue();
return new StringBuilder(res).insert(res.indexOf('=') + 2, Integer.valueOf(a + b).toString()).toString();
}
else {
String[] nums = expr.split("-");
int a = Integer.valueOf(nums[0]).intValue();
int b = Integer.valueOf(nums[1]).intValue();
return new StringBuilder(res).insert(res.indexOf('=') + 2, Integer.valueOf(a - b).toString()).toString();
}
}
public static void main(String[] args) {
PrintStream console = System.out;
ByteArrayOutputStream baos = new ByteArrayOutputStream(10);
System.setOut(new PrintStream(baos));
testString.printSomething();
System.setOut(console);
System.out.print(eval(baos.toString()).trim());
}
public static class TestString {
public void printSomething() {
System.out.println("3 + 6 = ");
}
}
}