Class Code 9/8/17

RefValEx.java

class TestClass {
    private int val;
    
    public TestClass(int val){
        this.val = val;
    }

    public int getVal(){
        return val;
    }

    public void setVal(int v){
        val = v;
    }   
}

public class RefValEx {
    public static void modifyRef(TestClass c){
        c.setVal(42);
    }

    public static void modifyVal(int i){
        i++;
    }

    public static void refVsVal(){
        int v = 19;
        int v2 = v;
        System.out.println("int v: " + v);
        v2++;
        System.out.println("int v: " + v);
        System.out.println("int v2: " + v2);
        
        TestClass tc = new TestClass(19);
        TestClass tc2 = tc;
        System.out.println("tc.getVal(): " + tc.getVal());
        tc2.setVal(47);
        System.out.println("tc.getVal(): " + tc.getVal());
        System.out.println("tc2.getVal(): " + tc2.getVal());

        // Examining reference equality.
        System.out.println("tc==tc2: " + (tc == tc2));
        TestClass tc3 = new TestClass(47);
        System.out.println("tc==tc3: " + (tc == tc3));
    }

    public static void passByRefVsVal(){
        int v = 19;
        System.out.println("int v: " + v);
        modifyVal(v);
        System.out.println("int v: " + v);

        TestClass tc = new TestClass(19);
        System.out.println("tc.getVal(): " + tc.getVal());
        modifyRef(tc);
        System.out.println("tc.getVal(): " + tc.getVal());
    }

    public static void main(String[] args){
        System.out.println("--- Ref vs. Val ---");
        refVsVal();
        System.out.println("--- Pass by ref vs. Pass by val ---");
        passByRefVsVal();
    }
}

class TestClass {

private int val;

public TestClass(int val){

this.val = val;

}

public int getVal(){

return val;

}

public void setVal(int v){

val = v;

}

public class RefValEx {

public static void modifyRef(TestClass c){

c.setVal(42);

}

public static void modifyVal(int i){

i++;

}

public static void refVsVal(){

int v = 19;

int v2 = v;

System.out.println("int v: " + v);

v2++;

System.out.println("int v: " + v);

System.out.println("int v2: " + v2);

TestClass tc = new TestClass(19);

TestClass tc2 = tc;

System.out.println("tc.getVal(): " + tc.getVal());

tc2.setVal(47);

System.out.println("tc.getVal(): " + tc.getVal());

System.out.println("tc2.getVal(): " + tc2.getVal());

// Examining reference equality.

System.out.println("tc==tc2: " + (tc == tc2));

TestClass tc3 = new TestClass(47);

System.out.println("tc==tc3: " + (tc == tc3));

}

public static void passByRefVsVal(){

int v = 19;

System.out.println("int v: " + v);

modifyVal(v);

System.out.println("int v: " + v);

TestClass tc = new TestClass(19);

System.out.println("tc.getVal(): " + tc.getVal());

modifyRef(tc);

System.out.println("tc.getVal(): " + tc.getVal());

}

public static void main(String[] args){

System.out.println("--- Ref vs. Val ---");

refVsVal();

System.out.println("--- Pass by ref vs. Pass by val ---");

passByRefVsVal();

}

EnumTest.java

// An adaptation of code from
// https://docs.oracle.com/javase/tutorial/java/javaOO/enum.html

public class EnumTest {
    public enum Day {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY }

    private Day day; 

    public EnumTest(Day day){
        this.day = day;
    }

    public void tellItLikeItIs() {
        switch (day) {
            case MONDAY:
                System.out.println("Mondays are bad.");
                break;
                    
            case FRIDAY:
                System.out.println("Fridays are better.");
                break;
                         
            case SATURDAY: case SUNDAY:
                System.out.println("Weekends are best.");
                break;
                        
            default:
                System.out.println("Midweek days are so-so.");
                break;

        }
    }

    public static void main(String[] args){
        EnumTest e = new EnumTest(Day.FRIDAY);
        e.tellItLikeItIs();
    }
}

// An adaptation of code from

// https://docs.oracle.com/javase/tutorial/java/javaOO/enum.html

public class EnumTest {

public enum Day {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY }

private Day day;

public EnumTest(Day day){

this.day = day;

}

public void tellItLikeItIs() {

switch (day) {

case MONDAY:

System.out.println("Mondays are bad.");

break;

case FRIDAY:

System.out.println("Fridays are better.");

break;

case SATURDAY: case SUNDAY:

System.out.println("Weekends are best.");

break;

default:

System.out.println("Midweek days are so-so.");

break;

}

public static void main(String[] args){

EnumTest e = new EnumTest(Day.FRIDAY);

e.tellItLikeItIs();

}

Hi There!

RefValEx.java

EnumTest.java