Added java version of the excersise

java/src/main/java/Invoice.java

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+import javax.swing.*;
+import java.util.List;
+
+public class Invoice {
+
+    public String customer;
+    public List<Performance> performances;
+
+    public Invoice(String customer, List<Performance> performances) {
+        this.customer = customer;
+        this.performances = performances;
+    }
+}

java/src/main/java/Performance.java

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+public class Performance {
+
+    public String playID;
+    public int audience;
+
+    public Performance(String playID, int audience) {
+        this.playID = playID;
+        this.audience = audience;
+    }
+}

java/src/main/java/Play.java

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+public class Play {
+
+    public String name;
+    public String type;
+
+    public Play(String name, String type) {
+        this.name = name;
+        this.type = type;
+    }
+}

java/src/main/java/StatementPrinter.java

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+import java.text.NumberFormat;
+import java.util.Locale;
+import java.util.Map;
+
+public class StatementPrinter {
+
+    public String print(Invoice invoice, Map<String, Play> plays) {
+        var totalAmount = 0;
+        var volumeCredits = 0;
+        var result = String.format("Statement for %s\n", invoice.customer);
+
+        NumberFormat frmt = NumberFormat.getCurrencyInstance(Locale.US);
+
+        for (var perf : invoice.performances) {
+            var play = plays.get(perf.playID);
+            var thisAmount = 0;
+
+            switch (play.type) {
+                case "tragedy":
+                    thisAmount = 40000;
+                    if (perf.audience > 30) {
+                        thisAmount += 1000 * (perf.audience - 30);
+                    }
+                    break;
+                case "comedy":
+                    thisAmount = 30000;
+                    if (perf.audience > 20) {
+                        thisAmount += 10000 + 500 * (perf.audience - 20);
+                    }
+                    thisAmount += 300 * perf.audience;
+                    break;
+                default:
+                    throw new Error("unknown type: ${play.type}");
+            }
+
+            // add volume credits
+            volumeCredits += Math.max(perf.audience - 30, 0);
+            // add extra credit for every ten comedy attendees
+            if ("comedy" == play.type) volumeCredits += Math.floor(perf.audience / 5);
+
+            // print line for this order
+            result += String.format("  %s: %s (%s seats)\n", play.name, frmt.format(thisAmount / 100), perf.audience);
+            totalAmount += thisAmount;
+        }
+        result += String.format("Amount owed is %s\n", frmt.format(totalAmount / 100));
+        result += String.format("You earned %s credits\n", volumeCredits);
+        return result;
+    }
+
+}

java/src/test/java/StatementPrinterTests.java

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+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StatementPrinterTests {
+
+    @Test
+    void printsStatements() {
+        Map<String, Play> plays = Map.of("hamlet", new Play("Hamlet", "tragedy"),
+                "as-like", new Play("As You Like It", "comedy"),
+                "othello", new Play("Othello", "tragedy"));
+
+        Invoice invoice = new Invoice("BigCo", List.of(new Performance("hamlet", 55),
+                new Performance("as-like", 35),
+                new Performance("othello", 40)));
+
+        StatementPrinter statementPrinter = new StatementPrinter();
+        var result = statementPrinter.print(invoice, plays);
+
+        assertThat(result).isEqualTo("Statement for BigCo\n" +
+                "  Hamlet: $650.00 (55 seats)\n" +
+                "  As You Like It: $580.00 (35 seats)\n" +
+                "  Othello: $500.00 (40 seats)\n" +
+                "Amount owed is $1,730.00\n" +
+                "You earned 47 credits\n");
+    }
+}