0x20Lesson 3 of 6

Calculate with expressions and strings

Use arithmetic operators and combine values to build output.

14 min 4-question quiz 1 code exercise

By the end of this lesson you can

Evaluate arithmetic and distinguish numeric addition from string concatenation.

Java supports arithmetic operators such as +, -, *, /, and % (remainder). When both operands are integers, division truncates the fractional part. The + operator adds numbers, and when a String is involved it can concatenate text. Parentheses make evaluation order clear.

Main.java

1int total = 17;
2int people = 5;
3System.out.println(total / people);
4System.out.println("Left: " + (total % people));

Output

3
Left: 2

Use a double when a calculation needs fractional values, or cast an operand before division. String concatenation is convenient for small messages; formatted output such as printf can control how numbers are displayed.

Key takeaways

Evaluate arithmetic and distinguish numeric addition from string concatenation.
Java checks types as it compiles your source.
Use compiler messages as clues about what needs fixing.

Lesson quiz

4 questions · pass with 3 correct · up to 50 XP

Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.

Practice: write Java

Write Java in the editor and run it against sample input with a remote compiler. Your code is sent to Compiler Explorer to compile and run.

Exercise 1

Convert Celsius to Fahrenheit

+25 XP

Read a Celsius temperature as a double and print Fahrenheit using F = C * 9 / 5 + 32. Keep the calculation in floating point.

Water freezes
Room temperature

Main.java

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Java is compiled and run by Compiler Explorer (godbolt.org), a free public service. Your source code and test input are sent to that service.

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