Constructor Questions 2

Question

Hi evryone! I'd like ask something

How can i also a default value also grass not only sky?
And how know that case(multiple variable) v2 that which variable will be green?

Thank you

Answer 1

The tag is used so when people do searches for posts it'll assist with generating appropriate results.

Here is your code with some edits from me: (Let me know if you need me to explain further)

https://code.sololearn.com/cvTpdrjVW2B6/#java

public class Earth {
private String sky;
private String grass;

Earth() {
this.sky = "Red";
this.grass = "Green";
}

Earth(String sky, String grass) {
this.sky = sky;
this.grass = grass;
}

// Setters
public void setSky(String sky) {
this.sky = sky;
}

public void setGrass(String grass){
this.grass = grass;
}

// Getters
public String getSky() {
return this.sky;
}

public String getGrass() {
return this.grass;
}
}

public class Program {
public static void main(String[] args) {
//color will be "Red" for Sky, "Green" for Grass
Earth v1 = new Earth();

//We will set whatever color we want
Earth v2 = new Earth("Blue", "Yellow");

// Lets display our values
System.out.println("V1's sky is " + v1.getSky() + " and grass is " + v1.getGrass());
System.out.println("V2's sky is " + v2.getSky() + " and grass is " + v2.getGrass());

// Lets use our setters to change values
v1.setSky("Pink");
v1.setGrass("Purple");
v2.setSky("Orange");
v2.setGrass("Black");

// Print new values
// Lets display our values
System.out.println("V1's sky is " + v1.getSky() + " and grass is " + v1.getGrass());
System.out.println("V2's sky is " + v2.getSky() + " and grass is " + v2.getGrass());
}
}

::: OUTPUT :::

V1's sky is Red and grass is Green
V2's sky is Blue and grass is Yellow
V1's sky is Pink and grass is Purple
V2's sky is Orange and grass is Black

Answer 2

If you could, post a link to your code. The link that you posted as a tag doesn't take me to any code but redirects back to Code Playground. Post up link and I'll take a look at it for you.

You can create a default constructor, as well as multiple constructors with parameters, to determine how your initial object will be once created. While I wait for your response, I'll create an example for you.

Answer 3

Here is an example. Sky is default when object is created, but you have option to set its type upon creation or change it afterwards.

Hope this helps.

https://code.sololearn.com/c9h5TlfzJcEF/#java

class myClass {
private String type;

// Default constructor
public myClass(){
this.type = "Sky"; // default will be Sky
}

// Another constructor - takes type as an argument
public myClass(String type){
this.type = type;
}

// setters
public void setType(String type){
this.type = type;
}

// getters
public String getType(){
return this.type;
}
}

public class Program
{
public static void main(String[] args) {
// Create objects from our class
myClass obj1 = new myClass();
myClass obj2 = new myClass("Grass");

// Print object's type member
System.out.println("Obj1 Type is " + obj1.getType());
System.out.println("Obj2 Type is " + obj2.getType());

// Use setter to change type
obj1.setType("Dirt");
obj2.setType("Sand");

// Print objects again to see changes
System.out.println("Obj1 Type is now " + obj1.getType());
System.out.println("Obj2 Type is now " + obj2.getType());
}
}

Answer 4

@Erik

Reference the second set of code I posted to you: https://code.sololearn.com/cvTpdrjVW2B6/#java

It's same concept, you're just changing the name of your variables is all. You would change leg, hand, etc.. in the same way that we were changing sky, grass, etc.. Replace Earth with Body, replace Sky with hand, replace Grass with leg. Then just make sure your variables match up throughout the code.

Answer 5

@Erik

You're welcome, Erik.

Earth() {
this.setSky("Red");
}

^In this example, you're using one of the setter methods to change your value to red.

Earth() {
this.sky="Red";
}

^This is setting the member's value directly without calling the method.

The end result would be the same, but how you're reaching the end is different. Since you're doing all of this from within the class itself, I prefer to directly set the variable since it's within scope, rather than calling a function and then doing exactly what I was doing. If it was outside of the class/scope, then that's when I use the setter method. This is more about consistency with what I program, but also about doing less things to reach the same thing, which often equates to better performance. However, in this example, if there is any type of performance gain, it's negligible gain.

As for the other section of code, the Earth() {} is the constructor, so you can set ALL of the initial values for your object's members. As such, any members of the class which you want to have a specific default values should be specified here. When you create an object, this portion of code is executed automatically and the member values will be set at that point. You can use parameters/arguments so that you can specify those values yourself from the code that you create the object at, which is where the other constructors I posted come into play.

Hope that makes sense. Let me know if I should explain it further.

Answer 6

What purpose the "tag" ?( I cant post anything while this empty.)
Here is my code the URL:
https://code.sololearn.com/cbb5ulCcgSYQ/#java

Thank you

Answer 7

Thank you your answer and your efforts.
1 But i would like know how can i change John and Jack not hand but leg.
2 And know what decide what will be change leg or hand from these:
John = new Body(); and this Body Jack = new Body("black");

thanks very much

Here is my code to metaphor

class Body {
private String hand;
private String leg;

// Default constructor
public Body(){
this.hand = "white"; // default will be Sky
}

// Another constructor - takes type as an argument
public Body(String hand){
this.hand = hand;
}

// setters
public void setHand(String hand){
this.hand = hand;
}

// getters
public String getHand(){
return this.hand;
}
}

public class Program
{
public static void main(String[] args) {
// Create objects from our class
Body John = new Body();
Body Jack = new Body("black");

// Print object's type member
System.out.println("John hand is " + John.getHand());
System.out.println("Jack hand is " + Jack.getHand());

// Use setter to change type
John.setHand("yellow");
Jack.setHand("brown");

// Print objects again to see changes
System.out.println("John hand is now " + John.getHand());
System.out.println("Jack hand is now " +Jack.getHand());
}
}

Answer 8

Thank you very much

and what is difference bettwen
Earth() {
setSky("Red");
}
or even
Earth() {
sky="Red";
}

and that solution that you use
Earth() {
this.sky = "Red";
this.grass = "Green";
}

Thank you

Answer 9

You are welcome!;-]

Answer 10

@ Jakob Marley
Thank you. It's very usefull

I'd like ask that what is the diffferent:

Earth() {
this.sky = "Red";
}

and

Earth() {
setSky("Red");
}

so without "this" somebody said me that i mustn't use "this."

thank you