Constructors Using Some Basic Examples in Java

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Constructors Using Some Basic Examples in Java

Constructors Using Some Basic Examples:

Constructors are the special methods whose name is the same as the class name.
Constructors do not have return types even void also.
Constructors will be invoked by the JVM automatically at the time of object creation.
Constructors are mainly used to initialize instance variables of class with a different set of values.

Examples:

Lab1.java

class Lab1 {
public static void main(String args[]) {
Student stu1 = new Student();
stu1.show();
Student stu2 = new Student();
stu2.show();
}
}
class Student {
intsid;
String sname;
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab2.java

class Lab2 {
public static void main(String args[]) {
Student stu = new Student();
stu.sid = 99;
stu.sname = "Ayush";
stu.show();
}
}
class Student {
intsid;
String sname;
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab3.java

class Lab3 {
public static void main(String args[]) {
Student stu = new Student();
stu.sid = 99;
stu.sname = "Ayush";
stu.show();
}
}
class Student {
intsid;
String sname;
Student() {
System.out.println("Student Default Constructor");
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab4.java

class Lab4 {
public static void main(String args[]) {
Student stu = new Student();
stu.sid = 99;
stu.sname = "Ayush";
stu.show();
}
}
class Student {
intsid;
String sname;
Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab5.java

class Lab5 {
public static void main(String args[]) {
Student stu1 = new Student(88, "Ayush");
stu1.show();
Student stu2 = new Student(99, "Garg");
stu2.show();
}
}
class Student {
intsid;
String sname;
Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab6.java

class Lab6 {
public static void main(String args[]) {
Student stu1 = new Student();
stu1.show();
Student stu2 = new Student(99, "Garg");
stu2.show();
}
}
class Student {
intsid;
String sname;
Student() {
System.out.println("Student Default Constructor");
}
Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab7.java

Lab8.java

class Lab8 {
public static void main(String args[]) {
Student stu3 = new Student(77, "AG");
stu3.show();
}
}
class Student {
intsid;
String sname;
Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
Student(int x, int y) {
System.out.println("Student 2-Arg constructor");
sid = x;
sname = y;
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab9.java

class Lab9 {
public static void main(String args[]) {
Student stu3 = new Student(77, "AG");
stu3.show();
}
}
class Student {
intsid;
String sname;
Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
Student(String y, int x) {
System.out.println("Student 2-Arg constructor");
sname = y;
sid = x;
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab10.java

class Lab10 {
public static void main(String args[]) {
Student stu = new Student();
stu.Student(77, "AG");
stu.show();
}
}
class Student {
intsid;
String sname;
Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
Student() {
System.out.println("Student default constructor");
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab11.java

class Lab11 {
public static void main(String args[]) {
Student stu = new Student();
stu.Student(77, "AG");
stu.show();
}
}
class Student {
intsid;
String sname;
void Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
Student() {
System.out.println("Student default constructor");
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab12.java

class Lab12 {
public static void main(String args[]) {
Student stu = new Student();
stu.Student(77, "AG");
stu.show();
}
}
class Student {
intsid;
String sname;
void Student(int id, Stringsn) {
System.out.println("Student 2-Arg Constructor");
sid = id;
sname = sn;
}
void show() {
System.out.println(sid + "\t" + sname);
}
}

Lab13.java

class Lab13 {
public static void main(String args[]) {
Student stu = new Student(-12);
stu.show();
}
}
class Student {
int age = 18;
Student(int ag) {
System.out.println("Student 2-Arg Constructor");
age = ag;
}
void show() {
System.out.println(age);
}
}

Lab14.java

class Lab14 {
public static void main(String args[]) {
Student stu = new Student(-12);
stu.show();
}
}
class Student {
int age = 18;
Student(int ag) {
System.out.println("Student 2-Arg Constructor");
if (ag = 18)
return;
age = ag;
}
void show() {
System.out.println(age);
}
}

Lab15.java

class Lab15 {
public static void main(String args[]) {
Student stu = new Student(-12);
stu.show();
}
}
class Student {
int age = 18;
Student(int ag) {
System.out.println("Student 2-Arg Constructor");
if (ag = 18)
return 0;
age = ag;
}
void show() {
System.out.println(age);
}
}