Java foundations

String  name   = "Dashboard";   // text
int     count  = 3;             // whole numbers
double  total  = 149.97;        // decimals
boolean shown  = true;          // true / false

expected.equals(actual)     // YES — compares text
expected == actual          // NO  — compares memory
name.contains("Dash")  name.length()  name.trim()

if (code == 200) { ... }
else if (code == 404) { ... }
else { ... }
==  !=  >  <  >=  <=     &&(and)  ||(or)  !(not)

for (String b : browsers) { ... }   // for each
for (int i = 1; i <= 3; i++) { ... } // counted
// while(...) repeats until false — needs a deadline!

static boolean isValidEmail(String email) {
    return email.contains("@");
}
// actions return void; questions return values

List<String> xs = new ArrayList<>();
xs.add("a");  xs.get(0);  xs.size();   // index from 0
Map<String,String> row = new HashMap<>();
row.put("user","qa");  row.get("user");
// List of Maps = your test-data spreadsheet

s.equals(t)   s.equalsIgnoreCase(t)
s.contains("x")  s.startsWith("h")  s.endsWith(".com")
s.trim()  s.toLowerCase()  s.replace("a","b")
s.length()  s.isEmpty()  s.split(",")
String.format("Cart: %d items, $%.2f", n, total)

int n    = Integer.parseInt("42");    // String -> int
double d = Double.parseDouble("9.99");
String s = String.valueOf(42);        // number -> String
// UI text is ALWAYS String — parse before doing math

incompatible types       value vs declared type
cannot find symbol       typo / wrong case / missing import
';' expected             check this line AND the one above
missing return statement a code path exits without return
non-static ... context   instance stuff called from static

public class TestUser {
    String username;                       // fields
    public TestUser(String u) {            // constructor
        this.username = u;
    }
    public boolean isAdmin() { ... }       // method
}
TestUser alice = new TestUser("alice");    // object