update:demo13

com/study/demo13/GradeService.java

@@ -0,0 +1,72 @@
+package com.study.demo13;
+
+interface ScoreCalculator {
+    double calculate();
+    String getLevel();
+}
+
+abstract class AbstractCourse implements ScoreCalculator {
+    protected double score;
+
+    public AbstractCourse(double score) {
+        this.score = score;
+    }
+
+    protected String levelByScore(double s) {
+        if (s >= 75) {
+            return "A";
+        } else if (s >= 60) {
+            return "B";
+        } else if (s >= 60) {
+            return "C";
+        } else {
+            return "D";
+        }
+    }
+}
+
+class TheoryCourse extends AbstractCourse {
+    public TheoryCourse(double score) {
+        super(score);
+    }
+
+    @Override
+    public double calculate() {
+        return score;
+    }
+
+    @Override
+    public String getLevel() {
+        return levelByScore(score);
+    }
+}
+
+class LabCourse extends AbstractCourse {
+    public LabCourse(double score) {
+        super(score);
+    }
+
+    @Override
+    public double calculate() {
+        return score * 0.9;
+    }
+
+    @Override
+    public String getLevel() {
+        return levelByScore(calculate());
+    }
+}
+
+public class GradeService {
+    public static void main(String[] args) {
+        ScoreCalculator theory = new TheoryCourse(85);
+        ScoreCalculator lab = new LabCourse(85);
+        ScoreCalculator theoryLow = new TheoryCourse(55);
+        ScoreCalculator labMid = new LabCourse(70);
+
+        System.out.println("TheoryCourse: score = " + theory.calculate() + ", level = " + theory.getLevel());
+        System.out.println("LabCourse: score = " + lab.calculate() + ", level = " + lab.getLevel());
+        System.out.println("TheoryCourse(low): score = " + theoryLow.calculate() + ", level = " + theoryLow.getLevel());
+        System.out.println("LabCourse(mid): score = " + labMid.calculate() + ", level = " + labMid.getLevel());
+    }
+}