String Concatenation

All 15 string concatenation questions

Work through the interactive quiz above first. This is the full string concatenation question set with worked solutions, so students can review any question after attempting it.

1. 1.Code Tracing 01 - String Concatenation: track the final printed value.

   String tag = "ALGO";
   int x = 18;
   int y = 3;
   int z = 5;
   System.out.print(tag + (x + y) + z);

   • ALGO1835
   • ALGO26
   • 215ALGO
   • ALGO215
   Show worked solution

   Correct answer: ALGO215

   The parenthesized addition happens before concatenation; z is appended after the String result already exists.

2. 2.Code Tracing 12 - String Concatenation: follow the variable updates.

   String label = "PR";
   int a = 26;
   int b = 5;
   int c = 7;
   System.out.print(a + b + label + c);

   • 31PR7
   • 265PR7
   • 38PR
   • PR317
   Show worked solution

   Correct answer: 31PR7

   The first two operands are ints, so they add numerically. Once label is reached, the rest is concatenation.

3. 3.Code Tracing 28 - String Concatenation: trace the branch and loop path.

   String out = "M";
   out += 38;
   out += (3 + 10);
   System.out.print(out);

   • M3813
   • M38310
   • M51
   • 3813
   Show worked solution

   Correct answer: M3813

   The first += appends a number as text. The parentheses force the second numeric addition before appending.

4. 4.Code Tracing 39 - String Concatenation: watch the index changes.

   String prefix = "AR";
   int a = 46;
   int b = 5;
   int c = 5;
   System.out.print(prefix + a + (b + c));

   • 46AR10
   • AR4610
   • AR56
   • AR4655
   Show worked solution

   Correct answer: AR4610

   prefix + a starts concatenation. The parenthesized expression is evaluated numerically before it is appended.

5. 5.Code Tracing 50 - String Concatenation: evaluate the state change step by step.

   String word = "CODING";
   int a = 54;
   int b = 7;
   String result = (a + b) + "-" + word.length();
   System.out.print(result);

   • 55
   • 6-61
   • 61-6
   • 547-6
   Show worked solution

   Correct answer: 61-6

   The arithmetic in parentheses happens first. The hyphen is a String, so the length is appended as text.

6. 6.What is printed by the following code segment?

   int a = 1;
   int b = 2;
   System.out.print("R" + a + b + " " + (a + b) + " " + a + b);

   • R3 3 3
   • R12 3 3
   • R12 3 12
   • R3 3 12
   Show worked solution

   Correct answer: R12 3 12

   Once a String appears everything to its right concatenates, unless parentheses force the addition first.

7. 7.What is printed by the following code segment?

   String s = "AP";
   s += 1 + 2;
   s += "" + 1 + 2;
   System.out.print(s);

   • AP1212
   • AP33
   • AP123
   • AP312
   Show worked solution

   Correct answer: AP312

   The first addition happens before the concatenation, giving 3. In the second, the empty string forces both digits to concatenate.

8. 8.What is printed by the following code segment?

   char c = 'A';
   System.out.print(c + 1);
   System.out.print(" " + c + 1);

   • 66 A1
   • A1 A1
   • 66 66
   • B B1
   Show worked solution

   Correct answer: 66 A1

   A char promotes to its numeric value in arithmetic, but concatenating with a String prints the character itself.

9. 9.What is printed by the following code segment?

   String s = "abc";
   System.out.print(s + s.length() + s.charAt(0));

   • abc3abc
   • abc3a
   • abc4a
   • abca3
   Show worked solution

   Correct answer: abc3a

   Both the length and the character are appended as text, in the order they appear.

10. 10.What is printed by the following code segment?

    double d = 5.0;
    System.out.print("v=" + d + 1);

    • v=6.0
    • v=51
    • v=5.01
    • v=6
    Show worked solution

    Correct answer: v=5.01

    The double prints with its decimal point and the 1 is concatenated afterward rather than added.

11. 11.What is printed by the following code segment?

    String a = "1";
    String b = "2";
    System.out.print(a + b + (a.length() + b.length()));

    • 1222
    • 14
    • 32
    • 122
    Show worked solution

    Correct answer: 122

    The strings concatenate to 12, and the parenthesised sum of the two lengths adds to 2.

12. 12.What is printed by the following code segment?

    System.out.print(1 + 2 + "3" + 4 + 5);

    • 3345
    • 12345
    • 15
    • 3 345
    Show worked solution

    Correct answer: 3345

    The leading operands are added because both are int, and everything after the String concatenates.

13. 13.What is printed by the following code segment?

    String s = "";
    for (int i = 3; i >= 1; i--)
    {
        s += i + "-";
    }
    System.out.print(s);

    • 1-2-3-
    • 3-2-1-
    • 321
    • -3-2-1
    Show worked solution

    Correct answer: 3-2-1-

    The loop counts down and appends each value with a trailing separator, so the result ends with a hyphen.

14. 14.What is printed by the following code segment?

    String s = "x";
    for (int i = 0; i < 3; i++)
    {
        s = s + s;
    }
    System.out.print(s.length());

    • 6
    • 4
    • 8
    • 3
    Show worked solution

    Correct answer: 8

    Each pass doubles the string, so its length goes 2, 4, then 8.

15. 15.What is printed by the following code segment?

    int n = 5;
    String s = n > 3 ? "big" : "small";
    System.out.print(s + n + (n > 3));

    • big5
    • bigtrue
    • small5true
    • big5true
    Show worked solution

    Correct answer: big5true

    The conditional operator selects big, the int concatenates as text, and the boolean prints as true.