Java.util Package Classes

Java.util.ArrayList

======================================================================

import java.util.ArrayList;

public class arrayList {

public static void main(String args[])

{

ArrayList<String> mylist= new ArrayList<String>();

mylist.add("sree");

mylist.add("krishna");

for(String str:mylist)

System.out.println(str);

}

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

        ArrayList<Integer> mylist= new ArrayList<Integer>();

        mylist.add(9);

        mylist.add(6);

        mylist.add(1);

        

            for(int x:mylist)

        System.out.println(x);

}

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist = new ArrayList<Integer>(5);

mylist.add(1);

mylist.add(2);

mylist.add(4);

mylist.add(5);

for(int x:mylist)

System.out.println(x);

System.out.println("===========");

mylist.add(2,3);  //index starts from zer0

for(int x: mylist)

System.out.println(x);

}

 

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

ArrayList<Integer> list1= new ArrayList<Integer>(5);

list1.add(1);

list1.add(2);

list1.add(3);

for(Integer x: list1)

System.out.println(x);

      System.out.println("===============");

      

      

      

   

      

   ArrayList<Integer> list2 =new ArrayList<Integer>(5);

   list2.add(4);

   list2.add(5);

   list2.add(6);

   

   

      

   

   for(Integer y:list2)

    System.out.println(y);

   System.out.println("===============");

   list1.addAll(list2);

   for(Integer x: list1)

System.out.println(x);

      System.out.println("===============");

      for(Integer y:list2)

    System.out.println(y);

   System.out.println("===============");

   

}

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

ArrayList<Integer> list1= new ArrayList<Integer>(5);

list1.add(1);

list1.add(5);

list1.add(6);

for(Integer x: list1)

System.out.println(x);

      System.out.println("===============");

      

      

      

   

      

   ArrayList<Integer> list2 =new ArrayList<Integer>(5);

   list2.add(2);

   list2.add(3);

   list2.add(4);

   

   

      

   

   for(Integer y:list2)

    System.out.println(y);

   System.out.println("===============");

   list1.addAll(1,list2);

   

   for(Integer y:list1)

    System.out.println(y);

   System.out.println("===============");

   

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist = new ArrayList<Integer>();

 

mylist.add(2);

mylist.add(5);

mylist.add(6);

System.out.println("size of the list: "+mylist.size());

mylist.clear();

System.out.println("size of the list: "+mylist.size());

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist =new ArrayList<Integer>(5);

mylist.add(5);

mylist.add(9);

mylist.add(21);

boolean isThere;

isThere=mylist.contains(9);

System.out.println(isThere);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist =new ArrayList<Integer>(5);

mylist.add(5);

mylist.add(9);

mylist.add(21);

mylist.add(34);

boolean isThere;

isThere=mylist.contains(9);

System.out.println(isThere);

System.out.println(mylist.size());

  int res=mylist.get(2);

  System.out.println("res: "+res);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<String> mylist = new ArrayList<String>(5);

mylist.add("a");

mylist.add("b");

mylist.add("c");

mylist.add("d");

int res= mylist.indexOf("b");

System.out.println(res);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<String> mylist = new ArrayList<String>(5);

mylist.add("a");

mylist.add("b");

mylist.add("c");

mylist.add("d");

mylist.add("c");

mylist.add("b");

mylist.add("c");

mylist.add("d");

int res= mylist.indexOf("b");

System.out.println(res);

boolean isEmpty;

isEmpty = mylist.isEmpty();

System.out.println(isEmpty);

for(String x:mylist)

System.out.println(x);

        int lastIndex;

lastIndex=mylist.lastIndexOf("c");

System.out.println(lastIndex);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList

{

public static void main(String args[])

{

ArrayList<Integer> mylist =new ArrayList<Integer>(5);

mylist.add(5);

mylist.add(9);

mylist.add(4);

System.out.println("size of the list: "+mylist.size());

for(Integer x: mylist)

{ System.out.print(x);System.out.print(",");

}    

mylist.remove(1);

System.out.println("size of the list: "+mylist.size());

for(Integer x: mylist)

{ System.out.print(x);System.out.print(",");

}    

}

}

======================================================================

java.util.HashMap

import java.util.HashMap;

public class hashMap {


public static void main(String args[])
{
HashMap mymap = new HashMap();

mymap.put(1, "apple");
mymap.put(2, "samsung");
mymap.put(3,"nokia");

System.out.println(mymap);

mymap.clear();

System.out.println(mymap);

}


}

======================================================================

import java.util.HashMap;

public class hashMap
{
public static void main(String args[])
{

    HashMap mymap = new HashMap();
    HashMap secnd = new HashMap();
 
     mymap.put(1, "english");
     mymap.put(2, "hindi");
     mymap.put(3, "telugu");
   
     System.out.println(mymap);
 
       secnd=(HashMap)mymap.clone();
   
      System.out.println(secnd);

}

}

======================================================================

import java.util.HashMap;

public class hashMap
{
public static void main(String args[])
{

    HashMap mymap = new HashMap();

 
     mymap.put(1, "english");
     mymap.put(2, "hindi");
     mymap.put(3, "telugu");
     mymap.put(5, "");
   
      System.out.println(mymap.containsKey(2));  //checks if key present
      System.out.println(mymap.containsValue("hindi"));  // checks if value present
   
   
   
   
   
 

}

}

======================================================================

import java.util.HashMap;
import java.util.Set;


public class hashMap{


public static void main(String args[])
{

HashMap test =new HashMap();

test.put(1, "C");
test.put(2, "c++");
test.put(3,"Java");

  Set myset=test.entrySet();

  System.out.println(myset);   //entry set
   
  System.out.println(test);    // printing normal map


}



}

======================================================================

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======================================================================

Java.util Package Classes

Java.util.ArrayList

======================================================================

import java.util.ArrayList;

public class arrayList {

public static void main(String args[])

{

ArrayList<String> mylist= new ArrayList<String>();

mylist.add("sree");

mylist.add("krishna");

for(String str:mylist)

System.out.println(str);

}

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

        ArrayList<Integer> mylist= new ArrayList<Integer>();

        mylist.add(9);

        mylist.add(6);

        mylist.add(1);

        

            for(int x:mylist)

        System.out.println(x);

}

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist = new ArrayList<Integer>(5);

mylist.add(1);

mylist.add(2);

mylist.add(4);

mylist.add(5);

for(int x:mylist)

System.out.println(x);

System.out.println("===========");

mylist.add(2,3);  //index starts from zer0

for(int x: mylist)

System.out.println(x);

}

 

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

ArrayList<Integer> list1= new ArrayList<Integer>(5);

list1.add(1);

list1.add(2);

list1.add(3);

for(Integer x: list1)

System.out.println(x);

      System.out.println("===============");

      

      

      

   

      

   ArrayList<Integer> list2 =new ArrayList<Integer>(5);

   list2.add(4);

   list2.add(5);

   list2.add(6);

   

   

      

   

   for(Integer y:list2)

    System.out.println(y);

   System.out.println("===============");

   list1.addAll(list2);

   for(Integer x: list1)

System.out.println(x);

      System.out.println("===============");

      for(Integer y:list2)

    System.out.println(y);

   System.out.println("===============");

   

}

}

======================================================================

import java.util.ArrayList;

class arrayList{

public static void main(String args[])

{

ArrayList<Integer> list1= new ArrayList<Integer>(5);

list1.add(1);

list1.add(5);

list1.add(6);

for(Integer x: list1)

System.out.println(x);

      System.out.println("===============");

      

      

      

   

      

   ArrayList<Integer> list2 =new ArrayList<Integer>(5);

   list2.add(2);

   list2.add(3);

   list2.add(4);

   

   

      

   

   for(Integer y:list2)

    System.out.println(y);

   System.out.println("===============");

   list1.addAll(1,list2);

   

   for(Integer y:list1)

    System.out.println(y);

   System.out.println("===============");

   

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist = new ArrayList<Integer>();

 

mylist.add(2);

mylist.add(5);

mylist.add(6);

System.out.println("size of the list: "+mylist.size());

mylist.clear();

System.out.println("size of the list: "+mylist.size());

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist =new ArrayList<Integer>(5);

mylist.add(5);

mylist.add(9);

mylist.add(21);

boolean isThere;

isThere=mylist.contains(9);

System.out.println(isThere);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<Integer> mylist =new ArrayList<Integer>(5);

mylist.add(5);

mylist.add(9);

mylist.add(21);

mylist.add(34);

boolean isThere;

isThere=mylist.contains(9);

System.out.println(isThere);

System.out.println(mylist.size());

  int res=mylist.get(2);

  System.out.println("res: "+res);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<String> mylist = new ArrayList<String>(5);

mylist.add("a");

mylist.add("b");

mylist.add("c");

mylist.add("d");

int res= mylist.indexOf("b");

System.out.println(res);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList{

public static void main(String args[])

{

ArrayList<String> mylist = new ArrayList<String>(5);

mylist.add("a");

mylist.add("b");

mylist.add("c");

mylist.add("d");

mylist.add("c");

mylist.add("b");

mylist.add("c");

mylist.add("d");

int res= mylist.indexOf("b");

System.out.println(res);

boolean isEmpty;

isEmpty = mylist.isEmpty();

System.out.println(isEmpty);

for(String x:mylist)

System.out.println(x);

        int lastIndex;

lastIndex=mylist.lastIndexOf("c");

System.out.println(lastIndex);

}

}

======================================================================

import java.util.ArrayList;

public class arrayList

{

public static void main(String args[])

{

ArrayList<Integer> mylist =new ArrayList<Integer>(5);

mylist.add(5);

mylist.add(9);

mylist.add(4);

System.out.println("size of the list: "+mylist.size());

for(Integer x: mylist)

{ System.out.print(x);System.out.print(",");

}    

mylist.remove(1);

System.out.println("size of the list: "+mylist.size());

for(Integer x: mylist)

{ System.out.print(x);System.out.print(",");

}    

}

}

======================================================================

java.util.HashMap

import java.util.HashMap;

public class hashMap {


public static void main(String args[])
{
HashMap mymap = new HashMap();

mymap.put(1, "apple");
mymap.put(2, "samsung");
mymap.put(3,"nokia");

System.out.println(mymap);

mymap.clear();

System.out.println(mymap);

}


}

======================================================================

import java.util.HashMap;

public class hashMap
{
public static void main(String args[])
{

    HashMap mymap = new HashMap();
    HashMap secnd = new HashMap();
   
     mymap.put(1, "english");
     mymap.put(2, "hindi");
     mymap.put(3, "telugu");
   
     System.out.println(mymap);
 
       secnd=(HashMap)mymap.clone();
     
      System.out.println(secnd);

}

}

======================================================================

import java.util.HashMap;

public class hashMap
{
public static void main(String args[])
{

    HashMap mymap = new HashMap();

   
     mymap.put(1, "english");
     mymap.put(2, "hindi");
     mymap.put(3, "telugu");
     mymap.put(5, "");
   
      System.out.println(mymap.containsKey(2));  //checks if key present
      System.out.println(mymap.containsValue("hindi"));  // checks if value present
     
     
   
   
   
   

}

}

======================================================================

======================================================================

Java methods

1)


-----------------------------------------------------------------


public class Employee {

String name;
int age;
String desg;
double sal;

   
public Employee(String name)
{
this.name=name;

}
public void empAge(int age)
{
this.age=age;
}

public void empDesg(String desg)
{
this.desg=desg;

}

  public void empSal(double sal)
  {
  this.sal=sal;

  }


void printEmployee()
{
System.out.println("Name : "+name);
System.out.println("Age : "+age);
System.out.println("Desg : "+desg);
System.out.println("Salary : "+sal);

}




}

------------------------------------------------------------



public class EmployeeTest{

public static void main(String args[])
{

Employee empOne=new Employee("sree");

empOne.empAge(24);
empOne.empDesg("developer");
empOne.empSal(11280.50);
empOne.printEmployee();

Employee empTwo=new Employee("krishna");

empTwo.empAge(21);
empTwo.empDesg("soft developer");
empTwo.empSal(11580);
empTwo.printEmployee();

}



}

----------------------------------------------------------------------------------------------------------------------

2)


public class FindMin {

public static void main(String args[])
{
int a,b,c;
a=5;
b=9;
c=minfn(a,b);
System.out.println("in main:"+c);

}

public static int minfn(int x, int y)
{
int min;
if (x>y)
min =y;
else min=x;
System.out.println(min);
return min;

}


}

--------------------------------------------------------------------------------------------------------------

3)

public class methodOver {

public static void main(String args[])

{

int a=3,b=4;

double c=1.3,d=3.5;

int res=minfn(a,b);

double resy=minfn(c,d);

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

System.out.println("double: "+resy);

}

 public static int minfn(int x,int y)

  {

 int min;

 if (x>y)

 min=y;

 else min=x;

 

 return min;

 

  }

public static double minfn(double a,double b)

{

double min;

  //a>b?min=b:min=a;

if(a>b)

min=b;

else min=a;

return min;

}

}

-------------------------------------------------------------------------------------------

4)

Stirng builder

public class HelloWorld {

    public static void main(String args[])
    {

        // String Builders

        StringBuilder sb= new StringBuilder();
        sb.append("Hello");
        System.out.println(sb);

        //string object can't modified        //string builder modifies original string
          StringBuilder s1=new StringBuilder("hello again!");
         System.out.println(s1);


        // specify intial capacity 5 chars in string build
         StringBuilder s2=new StringBuilder(5);
        System.out.println(s2);
        s2.append("hey back to java programming");
        System.out.println(s2);

        //capacity is flexible
        //find length        System.out.println(s2.length());


        //concatination          StringBuilder s3=new StringBuilder("Hello");
          s3.append("world");
        System.out.println(s3);

        s3.append("!");
        System.out.println(s3);



        // methods
        StringBuilder s4=new StringBuilder("Hello again");
        System.out.println(s4);


       //insert
        s4.insert(5,"2");
        System.out.println(s4);


        //replace
        s4.replace(5,s4.length()," world");
        System.out.println(s4);

        //delete        s4.delete(5,s4.length());
        System.out.println(s4);


        s4.append("abcdef ghijkl");
        System.out.println(s4);

        s4.delete(8,14);        /// Helloabcdef ghijkl        System.out.println(s4); // Helloabcijkl
        // delete char at
        System.out.println(s4.length());
          //s4.deleteCharAt(s4.lenght());

        //java.lang.StringBuilder.deleteCharAt         // here length is 12: indexes(0->11)        /*        s4.deleteCharAt(12);        System.out.println(s4);          */
        s4.deleteCharAt(11);
        System.out.println(s4);


           String s5="Hello world";
          for(int i=0;i<s5.length();i++)
          {
              System.out.println(s5.charAt(i));

          }




        String s6= "Hello from ";

        /// it won't modify the existing string by concatination        //we need to store the info in other string.
          String s8=s6.concat("sree");
        StringBuilder s7 = new StringBuilder("hey sree ");
        s7.append("wzzup");

        System.out.println(s6);
        System.out.println(s7);
        System.out.println(s8);


        s7.deleteCharAt(0);
        System.out.println(s7);

        //insert        s7.insert(0,"hie h");
        System.out.println(s7);

        // delete
         s7.delete(0,3);
        System.out.println(s7);


        /// repalce
          s7.replace(0,3,"hieee");
        System.out.println(s7);




        //converting to string
        int no=1024;
        String text=String.valueOf(no);
        System.out.println(text);

         System.out.println(text.substring(0,1));


          String flt=String.valueOf(24.56f);
          String dbl=String.valueOf(24.56);
          String bool=String.valueOf(true);

        System.out.println(flt);
        System.out.println(dbl);
        System.out.println(bool);


         String num="12345";
        System.out.println(num);
         int nob=Integer.parseInt(num);
        System.out.println(nob);

         //doble.parsedouble        //float.parse        //Boolean.parse

    }
}

Java String classes

public class HelloWorld {

    public static void main(String args[])
    {

        // Java string class methods        

        /*        String str="Hello World";
        // index finding        System.out.println(str.indexOf("o"));        System.out.println(str.indexOf("o",5));
        // char at index        System.out.println(str.charAt(7));
        //substring        System.out.println(str.substring(3));        System.out.println(str.substring(3,7));        System.out.println(str.contains("S"));
        //is empty        System.out.println(str.isEmpty());        System.out.println("".isEmpty());
        //upper lower        System.out.println(str.toUpperCase());        System.out.println(str.toLowerCase());
        //trim -> removes extra spaces at beg & end
        System.out.println("   hey...!  ".trim());
        // split -> spilts strings into array
        str="apple,nokia,samsung,lenovo";        str.split(",");

        System.out.println(str);
        // join        //str.join(",","apples","oranges,");
     */          String s1="";
        System.out.println(s1);
        System.out.println(s1.length());


        //java.lang.NullPointerException.        // a value was null & you're calling method on that
        /*        s1=null;        System.out.println(s1.length());        */

        s1=null;

        if(s1!=null)
            System.out.println(s1.length());
        else System.out.println("you have null string");



        // concatination of strings
           String s2="";

          s1="hey";
          s2="sree";
          String s3 = s1+" "+s2;
          System.out.println(s3);

        s1="hey";
        s2="hari";
        s3=s1.concat(s2);
        System.out.println(s3);



        // comparison of strings
          s1="Hello";
          s2="Hello";
          s3="hEllo";
          String s4=new String("Hello");

          System.out.println(s1==s2);
          System.out.println(s1==s4);
          System.out.println(s1.equals(s4));
          //use equals method when comparing the strings          //becz it compares the contents of strings

          System.out.println(s1.equalsIgnoreCase(s3));
          //ignores whether capital or small

        // Escape sequences
         s1="\"Hello\"";
         System.out.println(s1);

        s1="\'Hello\'";
        System.out.println(s1);

        s1="\nHello\n";
        System.out.println(s1);

        s1="\tHello\t";
        System.out.println(s1);



        s1="Java Programming";
        System.out.println(s1);
        System.out.println(s1.length());
        char first=s1.charAt(0);

        //  java.lang.StringIndexOutOfBoundsException        /*        char last=s1.charAt(16);        System.out.println(last);         */
        for (int i = 0; i <s1.length() ; i++) {
            System.out.print(s1.charAt(i));
            System.out.print(",");
        }

        System.out.println();

        int index=s1.indexOf('o');
        System.out.println(index);

        //prints -1 if it won't finds        index=s1.indexOf('Z');
        System.out.println(index);

       //index of string as well
        index=s1.indexOf("Pro");
        System.out.println(index);

        // find after skipping some chars
        index=s1.indexOf('a',10);
        System.out.println(index);


        // contains or not (return true or false)
        System.out.println(s1.contains("Pro"));
        System.out.println(s1.contains("pro"));

        // trim -> removes extra spaces        s2="   hey sree!   ";
        System.out.println(s2.trim());
        System.out.println(s2);


        s2="  programming  ";
        s3=s2.trim();
        System.out.println(s2);
        System.out.println(s3);



         s4="sree";
        System.out.println(s4.toUpperCase());
        System.out.println(s4);



        s1="Java Programming";
        s2=s1.substring(3);  //a Programming        System.out.println(s2);

        //  J a v a   P r o g r a m m i n g        //  0 1 2 3 4 5 6 7 8 9 10
        s2=s1.substring(3,6);  // a P        System.out.println(s2);



        // StringIndexOutOfBoundsException        /*        s2=s1.substring(25);  //a Programming        System.out.println(s2);

         */







    }
}