update,

it114105/itp4510/Lab01/Lab1.3/PartTimeStaff.java

@@ -0,0 +1,25 @@
+public class PartTimeStaff extends Staff implements Salary {
+    private int workingHour;
+
+    public PartTimeStaff(String name, int id, char grade, int workingHour) {
+        super(name, id, grade);
+        this.workingHour = workingHour;
+    }
+
+    public void display() {
+        System.out.println("Name: " + name + "; ID: " + id + "; Grade: " + grade + "; Working Hour: " + workingHour + "; Salary: " + computeSalary());
+    }
+
+    public int computeSalary() {
+        switch (grade) {
+            case 'A':
+                return SALARY_A;
+            case 'B':
+                return SALARY_B;
+            case 'C':
+                return SALARY_C;
+            default:
+                return SALARY_OTHER;
+        }
+    }
+}

it114105/itp4510/Lab01/Lab1.3/Salary.java

@@ -0,0 +1,8 @@
+public interface Salary {
+    public final int SALARY_A = 4000;
+    public final int SALARY_B = 3000;
+    public final int SALARY_C = 2000;
+    public final int SALARY_OTHER = 1000;
+
+    public abstract int computeSalary();
+}

it114105/itp4510/Lab01/Lab1.3/Staff.java

@@ -0,0 +1,13 @@
+public abstract class Staff {
+    protected String name;
+    protected int id;
+    protected char grade;
+
+    public Staff(String name, int id, char grade) {
+        this.name = name;
+        this.id = id;
+        this.grade = grade;
+    }
+
+    public abstract void display();
+}

it114105/itp4510/Lab01/Lab1.3/TestStaff.java

@@ -0,0 +1,8 @@
+public class TestStaff {
+    public static void main(String args[]) {
+        PartTimeStaff p1 = new PartTimeStaff("John", 123, 'B', 20);
+        PartTimeStaff p2 = new PartTimeStaff("Mary", 124, 'A', 22);
+        p1.display();
+        p2.display();
+    }
+}