Summary - Data types

Combine primitives, Math and BigDecimal to write an interest calculator.

Summary - Data types

In this group you learned Java's data types:

Primitive types: byte, short, int, long, float, double, char, boolean
Type casting: widening (automatic), narrowing (cast)
String concatenation: + operator
Math class: abs, max, min, pow, PI
BigDecimal: for precise money calculations

Now combine them and write an interest calculator.

Exercise Compute with Math

Write a Main class with a main method. Assign 15 to int a and 8 to int b. Print Math.max(a, b) with println.

Show example solution

public class Main {
    public static void main(String[] args) {
        int a = 15;
        int b = 8;
        System.out.println(Math.max(a, b));
    }
}

Tips

A few tips from this group:

Always use BigDecimal for money; double causes rounding loss.
Remember the L suffix on long: 10000000000L.
char uses single quotes, String uses double quotes.
The + operator works left to right; precedence matters.
Think about data loss before casting.

These basics are needed for conditionals and loops in the next groups.

Exercise Compute interest with BigDecimal

Write a Main class with a main method. Add import java.math.BigDecimal; at the top. Assign BigDecimal.valueOf(1000) to BigDecimal principal and BigDecimal.valueOf(0.05) to BigDecimal rate. Print principal.multiply(rate) with println.

Show example solution

import java.math.BigDecimal;

public class Main {
    public static void main(String[] args) {
        BigDecimal principal = BigDecimal.valueOf(1000);
        BigDecimal rate = BigDecimal.valueOf(0.05);
        System.out.println(principal.multiply(rate));
    }
}

Test yourself

Match the types

int

Integer
double

Decimal
char

Character
BigDecimal

Precise

Cast to convert

int whole = ____ 9.99;

Show answer

int whole = (int) 9.99;

Next lesson: Project design

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