Numbers and text together

+ has two jobs: it adds numbers, and it joins text. Java decides which one each + does, working from left to right. As soon as one side is a String, the + joins, and the result is a String again.

int a = 3;
int b = 4;
System.out.println("Total: " + a + b);
System.out.println("Total: " + (a + b));
System.out.println(a + b + " is the total");

Total: 34
Total: 7
7 is the total

• In the first line, "Total: " + a is text, Total: 3, and adding b to text joins it: Total: 34.
• In the second line the parentheses make a + b a calculation first.
• In the third line the two numbers come first, so they're added before any text appears.

Numbers have limits

An int can hold values up to 2147483647. A calculation that goes past the limit doesn't stop with an error: it wraps around to the negative end of the range and counts on from there, which is called overflow. One past the limit is the most negative int:

int big = 2147483647;
big = big + 1;
System.out.println(big);

-2147483648

The numbers in this course stay far from that limit, but it's worth knowing that it exists.