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Hausaufgabe 1 fertig #17

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93 changes: 81 additions & 12 deletions src/main/java/htw/berlin/prog2/ha1/Calculator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,11 @@ public class Calculator {

private String latestOperation = "";

// --- NEU für wiederholtes "=" -----------------------------------------
private double lastOperand = Double.NaN; // <<< NEW: merkt den zuletzt benutzten 2. Operanden
private String lastOperator = ""; // <<< NEW: merkt den zuletzt benutzten Operator


/**
* @return den aktuellen Bildschirminhalt als String
*/
Expand Down Expand Up @@ -60,7 +65,19 @@ public void pressClearKey() {
* @param operation "+" für Addition, "-" für Substraktion, "x" für Multiplikation, "/" für Division
*/
public void pressBinaryOperationKey(String operation) {
latestValue = Double.parseDouble(screen);
if ("*".equals(operation)) operation = "x";

double current = Double.parseDouble(screen);

// FALL: Es gibt bereits einen Operator, aber der 2. Operand wurde NOCH NICHT eingegeben
// -> nur den Operator austauschen (kein Rechnen, kein Zustand sonst ändern)
if (!latestOperation.isEmpty() && latestValue == current) {
latestOperation = operation;
return;
}

// normaler Fall: ersten Operanden übernehmen und Operator setzen
latestValue = current;
latestOperation = operation;
}

Expand Down Expand Up @@ -118,16 +135,68 @@ public void pressNegativeKey() {
* und das Ergebnis direkt angezeigt.
*/
public void pressEqualsKey() {
var result = switch(latestOperation) {
case "+" -> latestValue + Double.parseDouble(screen);
case "-" -> latestValue - Double.parseDouble(screen);
case "x" -> latestValue * Double.parseDouble(screen);
case "/" -> latestValue / Double.parseDouble(screen);
default -> throw new IllegalArgumentException();
};
screen = Double.toString(result);
if(screen.equals("Infinity")) screen = "Error";
if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
if(screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);
if (latestOperation == null) latestOperation = "";
if (lastOperator == null) lastOperator = "";

double current = Double.parseDouble(screen);

// Fall A: aktiver Operator vorhanden -> erste Ausführung (z. B. 2 + 3 = 5)
if (!latestOperation.isEmpty()) {
double result = switch (latestOperation) {
case "+" -> latestValue + current;
case "-" -> latestValue - current;
case "x" -> latestValue * current;
case "/" -> {
if (current == 0.0) {
screen = "Error";
latestOperation = "";
yield Double.NaN; // ✅ use yield instead of return
}
yield latestValue / current;
}
default -> throw new IllegalArgumentException();
};

screen = Double.toString(result);
if (screen.equals("Infinity") || screen.equals("-Infinity") || screen.equals("NaN")) screen = "Error";
if (screen.endsWith(".0")) screen = screen.substring(0, screen.length() - 2);
if (screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);

// Für wiederholtes "=" merken
lastOperand = current;
lastOperator = latestOperation;

// Ergebnis als Basis; aktiven Operator „verbrauchen“
latestValue = result;
latestOperation = "";
return;
}

// Fall B: Kein aktiver Operator -> letzte Operation wiederholen (z. B. 5 = -> 8)
if (!lastOperator.isEmpty() && !Double.isNaN(lastOperand)) {
double base = Double.parseDouble(screen);

double result = switch (lastOperator) {
case "+" -> base + lastOperand;
case "-" -> base - lastOperand;
case "x" -> base * lastOperand;
case "/" -> {
if (lastOperand == 0.0) {
screen = "Error";
yield Double.NaN; // ✅ use yield instead
}
yield base / lastOperand;
}

default -> throw new IllegalArgumentException();
};

screen = Double.toString(result);
if (screen.equals("Infinity") || screen.equals("-Infinity") || screen.equals("NaN")) screen = "Error";
if (screen.endsWith(".0")) screen = screen.substring(0, screen.length() - 2);
if (screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);

latestValue = result; // Basis für weiteres "="
}
}
}
47 changes: 47 additions & 0 deletions src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,53 @@ void testMultipleDecimalDots() {

assertEquals(expected, actual);
}
@Test
@DisplayName("should subtract two positive numbers correctly")
void testSimpleSubtraction() {
Calculator calc = new Calculator();

calc.pressDigitKey(9);
calc.pressBinaryOperationKey("-");
calc.pressDigitKey(4);
calc.pressEqualsKey();

assertEquals("5", calc.readScreen());
}

@Test
@DisplayName("should repeat last operation when pressing equals multiple times")
void testRepeatOperation() {
Calculator calc = new Calculator();

calc.pressDigitKey(2);
calc.pressBinaryOperationKey("+");
calc.pressDigitKey(3);
calc.pressEqualsKey(); // 2 + 3 = 5
calc.pressEqualsKey(); // should repeat +3 => 8

String expected = "8";
String actual = calc.readScreen();

assertEquals(expected, actual);
}
@Test
@DisplayName("should use the new operator if user changes it before entering second operand")
void testChangeOperatorBeforeSecondOperand() {
Calculator calc = new Calculator();

calc.pressDigitKey(7);
calc.pressBinaryOperationKey("+");
calc.pressBinaryOperationKey("*"); // Nutzer ändert Meinung: + -> *
calc.pressDigitKey(3);
calc.pressEqualsKey();

String expected = "21"; // 7 * 3
String actual = calc.readScreen();

assertEquals(expected, actual);
}




//TODO hier weitere Tests erstellen
Expand Down