Concatenation in java?

Question

In PHP you can concatenate strings with .= so that the string grows with what ever you add to it. I wonder if this could be done in java? I made some test in this code, to add all number into one long string, but not working! Could it be done in some other way?

int number = 100;
for (int x = number; x <= 2; x--) {

    resultat = resultat + Integer.toString(x);
}

Answer 1

Yes, += in Java is .= in PHP:

result += Integer.toString(x) . You just need to define String resultat = "" above the loop. (And as others noted - fix your loop condition, it's always false)

However, in loops you'd better use a StringBuilder . A String is immutable, so every time you use + a new string is created (which may be inefficient with bigger loops). Instead:

StringBuilder builder = new StringBuilder();
for (...) {
    builder.append(x);
}
String result = builder.toString();

Answer 2

x <= 2 is never true for x = 100 ...

You have to change the condition to x >= 2

But you can use +=

Answer 3

Your for loop just needs a bit of work. You've currently got x <= 2 when it should be x >= 2 otherwise the loop will never run as 100 is never smaller than 2!

Answer 4

It doesn't work in your example because you got the terminating condition of the for loop wrong. You should write it like this:

String resultat = "";
int number = 100;
for (int x = number; x >= 2; x--) {
  resultat = resultat + Integer.toString(x);
}

A for loop is roughly a while loop with some little extras. That's why you have to write the condition like this.

Answer 5

Try to use StringBuilder.append like this

    int number = 100;
    StringBuilder builder = new StringBuilder();
    for (int x = number; x <= 2; x--) {
        builder.append(x);
    }
    String result = builder.toString();