String.valueOf(int i) and Integer.toString(int i) can be used to convert int data type value into a String object
int x = 100;
String s = String.valueOf(100);
//OR
String s = Integer.toString(100);Integer.valueOf(String s) returns an instance of Integer class, while Integer.parseInt(String s) returns a variable of int data type!
String s = "100";
Integer k = Integer.valueOf(s);
//OR
int kk = Integer.parseInt(s);int intValue = 123456789;
String stringValue = Integer.toString(intValue);
int[] input = new int[stringValue.length()];
int inputLength = input.length;
for(int i=0; i<inputLength; i++){
input[i] = Character.getNumericValue(stringValue.charAt(i));
}See the CASES mentioned in the main class!
import java.util.*;
class PreTest {
public void callMe(){
System.out.println("Method of SUPER CLASS is called");
}
}
public class Test extends PreTest {
public void callMe(){
System.out.println("Method of SUB CLASS is called");
}
public static void main(String[] args){
/*CASE 1*/
Test obj = new Test();
PreTest obj2 = (PreTest) obj;
obj2.callMe();
/*----OUTPUT: Method of SUB CLASS is called----*/
/*CASE 2*/
PreTest obj3 = new PreTest();
//Test obj4 = (PreTest) obj3; /*--Not Valid--*/
/*CASE 3*/
//Test obj5 = new PreTest(); /*--Not Valid--*/
/*CASE 4*/
PreTest obj6 = new Test();
obj6.callMe();
/*----OUTPUT: Method of SUB CLASS is called----*/
/*CASE 5*/
PreTest obj7 = new PreTest();
//Test obj8 = (PreTest) obj7; /*--Even subclass object can not refer to a super class object--*/
}
}import java.util.*;
class TestTaker{
public int id;
String name;
public int marks;
public TestTaker(int id, String name, int marks) {
this.id = id;
this.name = name;
this.marks = marks;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public int getMarks() {
return marks;
}
}
public class Test
{
public static void main(String[] args){
List<TestTaker> list = new ArrayList<TestTaker>();
TestTaker obj1 = new TestTaker(1, "David", 91);
TestTaker obj2 = new TestTaker(2, "Mike", 93);
TestTaker obj3 = new TestTaker(3, "John", 95);
TestTaker obj4 = new TestTaker(4, "Sky", 95);
TestTaker obj5 = new TestTaker(5, "Leo", 99);
list.add(obj1);
list.add(obj2);
list.add(obj3);
list.add(obj4);
list.add(obj5);
Collections.sort(list,new MarksComparator());
for(TestTaker t : list){
System.out.println(t.getId()+" "+t.getName()+" "+t.getMarks());
}
}
}
class MarksComparator implements Comparator{
public int compare(Object obj1,Object obj2){
TestTaker t1=(TestTaker)obj1;
TestTaker t2=(TestTaker)obj2;
if(t1.marks==t2.marks)
return t1.name.compareTo(t2.name);
else if(t1.marks>t2.marks)
return -1;
else
return 1;
}
}
class NameComparator implements Comparator{
public int compare(Object obj1,Object obj2){
TestTaker t1=(TestTaker)obj1;
TestTaker t2=(TestTaker)obj2;
return t1.name.compareTo(t2.name);
}
}Approach 1 is also known as Anonymous comparator
/*---- Approach 1 ----*/
/*-- Using Anonymous comparators --*/
Collections.sort(list, new Comparator() {
public int compare(Object obj1,Object obj2){
TestTaker t1=(TestTaker)obj1;
TestTaker t2=(TestTaker)obj2;
if(t1.marks==t2.marks)
return t1.name.compareTo(t2.name);
else if(t1.marks>t2.marks)
return -1;
else
return 1;
}});
/*---- Approach 2 ----*/
Collections.sort(list,new MarksComparator());
/*-- Then write a separate Class --*/
class MarksComparator implements Comparator{
public int compare(Object obj1,Object obj2){
TestTaker t1=(TestTaker)obj1;
TestTaker t2=(TestTaker)obj2;
if(t1.marks==t2.marks)
return t1.name.compareTo(t2.name);
else if(t1.marks>t2.marks)
return -1;
else
return 1;
}
}public class Test{
public static <E extends Number> int addObjects(E a, E b){
return (a.intValue() + b.intValue());
/* intValue is a methos of Number class */
}
public static void main(String[] args){
System.out.println(addObjects(10, 20));
}
}public class Test{
public static <E extends Comparable> E addObjects(E a, E b){
if(a.compareTo(b)>0)
return a;
if(a.compareTo(b)<0)
return b;
else
return a;
}
public static void main(String[] args){
System.out.println("The larger value is: "+addObjects("Hello", "Jack"));
}
}
\drepresents any digit in regular expression but\is also a character in java so to convert\into a literal we add another\so that\dcan be considered as literal in regular expression!
Check all these regular expressions on a Java program
| SN | Java Regex String | Description |
|---|---|---|
| 1 | [A-Za-z] |
It matches a single character with all the uppercase and lowercase characters |
| 2 | [A-Za-z]? |
It matches zero or one character with all the uppercase and lowercase characters |
| 3 | [A-Za-z]* |
It matches zero or more than zero characters with all the uppercase and lowercase characters |
| 4 | [^A-Za-z]+ |
It matches a single or more characters with everything except A-Za-z |
| 5 | [^A-Za-z]{2} |
It matches exactly two characters with everything except A-Za-z |
| 6 | [A-Za-z0-9] |
It matches all the uppercase and lowercase alphanumeric characters |
| 7 | [A-Za-z0-9]{1,5} |
It matches minimum 1 and maximum 5 uppercase and lowercase alphanumeric characters |
| 8 | [A-Za-z !,?._'@]+ |
It matches 1 or more than 1 lowercase and uppercase alphabets along with special characters |
| 9 | [-+.^:,] |
It matches a single character with all the special characters |
| 10 | . |
It matches with a character of any kind |
| 11 | \\d{1} |
It matches with a single digit |
| 12 | \\d{1,3} |
It matches with a numerical value having 1 to 3 digits |
| 13 | [\\d]{1} |
It matches with a single digit |
| 14 | [0-5] |
It matches with a single digit ranging from 0 to 5 |
| 15 | \\s |
It matches with single white space character |
| 16 | [\\s] |
It matches with single white space character |