Add Java assignments to the repository

.gitignore: The build files, files left by editors like *~ and the PDF
documents for the assignments are to be ignored for the purposes of
version control.

README.rst: Rewrite, with one line description in Chinese.

java/alist.txt: List of assignments, sorted in the order of the list of
assignments, with the ones with completed documentation marked with `#`.

java/buildall: Script that will build all of the assignments into one
PDF file; to be rehauled for the final document.

code/*.java: The Java source code for the assignments.

dbld: Script that builds a PDF document for a single assignment.

index.typ: The list of assignments, subject to update for further
refinement and inclusion of yet more assignments.

jbld: Script that compiles code for a single Java assignment.

output/*.typ: Typst file containing the output (sessions) obtained from
running the individual Java assignments.

state.sql: Future alternative to `alist.txt`, under development.

template.typ: The Typst template used across all of assignment,
containing common code for the uniform styling, such as page border.

text/*.typ: Typst file documenting each Java assignment.

vendor/Java.sublime-syntax: Updated Sublime Text syntax file for Java,
used for newer syntax features, such as `var`, not yet available in
syntaxes shipped with Typst.

vendor/gr.tmTheme: A grayscale TextMate theme to be used for code in the
documents generated by Typst suitable for black and white printing.

wltd: Difference between the files in `code/` and `text/`, and `code/`
and `output`; need to be rewritten along with `state.sql`.

1 files changed, 55 insertions, 0 deletions

diff --git a/java/code/ConeCalculations.java b/java/code/ConeCalculations.java
new file mode 100644
index 0000000..1b8e64c
--- /dev/null
+++ b/java/code/ConeCalculations.java
@@ -0,0 +1,55 @@
+import java.util.Scanner;
+import java.util.InputMismatchException;
+
+class Cone {
+    double radius, height;
+    Cone(double r, double h) {
+        radius = r;
+        height = h;
+    }
+    double volume() {
+        return Math.PI * radius * radius * height / 3.0;
+    }
+    double surfaceArea() {
+        return Math.PI * radius * (radius + Math.sqrt(height * height + radius * radius));
+    }
+    void display() {
+        System.out.println("A cone with radius " + radius + " units and height " + height + " units has surface area " + surfaceArea() + " square units and volume " + volume() + " cubic units.");
+    }
+}
+
+class ConeCalculationsCLI {
+    public static void main(String args[]) {
+        if (args.length != 2) {
+            System.err.println("Usage: ConeCalculationsCLI radius height");
+            System.exit(1);
+        }
+        try {
+            var radius = Double.parseDouble(args[0]);
+            var height = Double.parseDouble(args[1]);
+            var c = new Cone(radius, height);
+            c.display();
+        } catch (NumberFormatException e) {
+            System.err.println("Invalid number given as input");
+            System.exit(1);
+        }
+    }
+}
+
+class ConeCalculationsScan {
+    public static void main(String args[]) {
+        try {
+            var sc = new Scanner(System.in);
+            System.out.print("Enter radius: ");
+            var radius = sc.nextDouble();
+            System.out.print("Enter height: ");
+            var height = sc.nextDouble();
+            var c = new Cone(radius, height);
+            c.display();
+        } catch (InputMismatchException e) {
+            System.err.println("Invalid number given as input");
+            System.exit(1);
+        }
+    }
+}
+