# 40+ Examples of User Defined Methods in Java with Explanation original

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Information about 40+ Examples of User Defined Methods in Java with Explanation original
Education

Published on February 21, 2014

Author: hrithikk

Source: authorstream.com

User Defined Methods in Java: User Defined Methods in Java With Animation Index: Index Advantages Simple Programs using Methods Add two numbers Average of three numbers Circle area Fahrenheit to Celsius Check number is even or not Check number is prime or not Reverse of a number Check number is palindrome or not Count number of digits in a number Sum of digits LCM of 2, 3 and 4 numbers HFC of 2 numbers 1 to 100 prime numbers 200 to 500 prime and palindrome Decimal to binary, octal, hex Binary to decimal, octal, hex Octal to binary,decimal , hex Hexadecimal to binary, octal, decimal Pass Array to Methods Print all elements of an array Sum of an array Average of an array Maximum element of an array Minimum element of an array Returning Array From Methods Reverse array Reverse every element of an array Function v/s Method: Function v/s Method Q .)What is the difference between a function and a method.? Ans.) A method is a function that is written in a class . We do not have functions in java; instead we have methods. This means whenever a function is written in java. It should be written inside the class only. But if we take C++, we can write the functions inside as well as outside the class. So in C ++, they are called member functions and not methods. Function with no arguments and no return(no input no output): No arguments here Function with no arguments and no return(no input no output) void display () { System.out.println ("this is inside method body"); } Name of the function is “display” When you want to return no value, then set return type to void Complete Program: Complete Program public class function1 { static void display() { System.out.println ("this is inside method body"); } public static void main(String args []) { System.out.println ("before function call"); display(); System.out.println ("after function call"); } } Method Definition Method Calling Add two integer numbers: Add two integer numbers int add( int a, int b) { int c= a+b ; return c; } Two Integer Arguments Returning integer value to calling method Complete Program: Complete Program public class function1 { static int add( int a, int b) { int c= a+b ; return c ; } public static void main(String args []) { System.out.println (add(45,67)); } } Display method is called method , because it is called by main method m ain method is calling method , because it is calling display method. Average of three integer numbers: M ethod S ignature —the method's name and the parameter types. Average of three integer numbers double avg ( int a, int b, int c ) { double d; d=((double) a+b+c )/3; return d; } This method takes multiple arguments and returns single value Calculate circle Area: Calculate circle Area double circleArea (float radius) { double area= Math.PI *radius*radius ; return area; } M ethod S ignature —the method's name and the parameter types. Convert Fahrenheit to Celsius: Convert Fahrenheit to Celsius double convertFahToCel (double fah ) { double cel =(fah-32)*5/9; r eturn cel ; } This method takes one argument and returns single value Check number is even or not: M ethod S ignature —the method's name and the parameter types. Check number is even or not boolean checkEven ( int n) { if(n%2==0) { return true; } else { return false; } } Check number is prime or not: Check number is prime or not boolean isPrime ( int n) { int i; for( i=2;i< n ;i ++) { if( n %i ==0) { break; } }d if(n==i) { return true; } else { return false; } } Reverse number: Reverse number int reverseNumber ( int n) { int x=0; for( ; n!=0 ; ) { int r=n%10; x=x*10+r; n=n/10; } return x ; } Check number is palindrome or not: C heck number is palindrome or not boolean isPalindrome ( int n) { int rev = reverseNumber (n) ; if(n==rev) { return true; } else { return false; } } Using previous slide’s reverse number method FOCUS ON ONE WORK We need to focus on palindrome not on reverse number code, this is a advantage of method. Count number of digits in a number: Count number of digits in a number This is Exercise Sum of digits: Sum of digits This is Exercise LCM(Lowest Common Multiple) of 2 numbers: LCM(Lowest Common Multiple) of 2 numbers long getLCM ( int n1, int n2) { long answer=1; for( int i=2;n1!=1 && n2!=1;) { if(n1%i ==0 && n2%i==0) { n1=n1/i ; n2=n2/i ; answer=answer*i ; } else if(n1%i==0) { n1=n1/i; answer=answer*i; } else if(n2%i==0) { n2=n2/i; answer=answer*i; } else { i++; } }//end of for loop answer=n1*n2*answer ; return answer; }//end of this method LCM of 3 Numbers: User Defined getLCM () 2 argument method LCM of 3 Numbers long getLCM ( int n1,int n2,int n3) { long result1 = getLCM (n1,n2); long finalResult = getLCM (( int ) result1,n3 ); return finalResult ; } Method overloading on getLCM () method differ by number of arguments Narrowing type conversion LCM of 4 Numbers: User Defined getLCM () 3 arguments method LCM of 4 Numbers long getLCM ( int n1,int n2,int n3, int n4) { long result1 = getLCM (n1,n2,n3); long finalResult = getLCM (( int ) result1,n4); return finalResult ; } Method overloading on getLCM () method differ by number of arguments Narrowing type conversion HCF(Highest Common Factor) of 2 numbers: HCF(Highest Common Factor) of 2 numbers int getHCF ( int n1,int n2) { int lcmOfThese =( int ) getLCM (n1,n2); long product=n1*n2; int hcfOfThese =( int )(product/ lcmOfThese ); return hcfOfThese ; } Narrowing type conversion /manual type casting/ down casting User Defined getLCM () method Print prime numbers between 1 and 100: Print prime numbers between 1 and 100 void printPrime1To100() { for( int i=1;i<=100;i++) { if( isPrime (i ) ==true) { System.out.println (i ); } } } User defined method Print prime numbers between 200 and 500 which are Palindrome numbers too: Print prime numbers between 200 and 500 which are Palindrome numbers too This is exercise Convert Decimal to XXX: Convert Decimal to XXX String convertDecimalToXXX (long n,int base) { StringBuilder sb = new StringBuilder (); for (;n!=0;n=n/base) { byte x= (byte)( n%base ); if(x >=10) { char ch =' '; switch(x ) { case 10:ch=' A';break ; case 11:ch=' B';break ; case 12:ch=' C';break ; case 13:ch=' D';break ; case 14:ch=' E';break ; case 15:ch=' F';break ; } sb.append ( ch ); } else { sb.append (x ); } } return String.valueOf ( sb.reverse ()); } Convert Decimal to Binary: Convert Decimal to Binary String convertDecimalToBinary (long n) { int base=2; String ans = convertDecimalToXXX ( n,base ); return ans ; } User defined method Convert Decimal to Octal: Convert Decimal to Octal String convertDecimalToOctal (long n) { int octal_base =8; String ans = convertDecimalToXXX ( n,octal_base ); return ans ; } User defined method Convert Decimal to Hexadecimal: Convert Decimal to Hexadecimal User defined method String convertDecimalToHexadecimal (long n) { int hex_base =16 ; String ans = convertDecimalToXXX ( n,hex_base ); return ans ; } Convert Binary to XXX: Convert Binary to XXX long convertXXXToDecimal ( int base,String num ) { StringBuilder sb = new StringBuilder ( num ); long sum=0,t=0; for( int i= sb.length ()-1;sb.length()!=0;i--,t++) { Character x= sb.charAt (i); int y=x-48; sb = sb.deleteCharAt (i ); double z=y*( Math.pow (base, t)); sum=sum +(long)z; } return sum; } Convert Binary to Decimal: Convert Binary to Decimal long convertBinaryToDecimal (String binary_number ) { int binary_base =2; long ans = convertXXXToDecimal ( binary_base,binary_number ); return ans ; } User defined method Convert Octal to Decimal: Convert Octal to Decimal long convertOctalToDecimal (String binary_number ) { int binary_base =8; long ans = convertXXXToDecimal ( binary_base,binary_number ); return ans ; } User defined method Convert Hexadecimal to Decimal: Convert Hexadecimal to Decimal User defined method long convertHexToDecimal (String binary_number ) { int binary_base =2; long ans = convertXXXToDecimal ( binary_base,binary_number ); return ans ; } Convert Hexadecimal to Octal: Convert Hexadecimal to Octal String convertHexToOctal (String hexNumber ) { long decimal= convertHexToDecimal ( hexNumber ); String ans = convertDecimalToOctal (decimal); return ans ; } User defined method Convert Hexadecimal to Binary: User defined method Convert Hexadecimal to Binary String convertHexToBinary (String hexNumber ) { long decimal= convertHexToDecimal ( hexNumber ); String ans = convertDecimalToBinary (decimal); return ans ; } Convert Octal to Hexadecimal: Convert Octal to Hexadecimal User defined method String convertOctalToHex (String octalNumber ) { long decimal= convertOctalToDecimal ( octalNumber ); String ans = convertDecimalToHex (decimal); return ans ; } Convert Octal to Binary: Convert Octal to Binary User defined method String convertOctalToBinary (String octalNumber ) { long decimal= convertOctalToDecimal ( octalNumber ); String ans = convertDecimalToBinary (decimal); return ans ; } Pass Array to Called Method: Pass Array to Called Method Print All elements of an Array: Print All elements of an Array void arrayTraversing ( int arr []) { for( int x:arr) { System.out.println (x); } } Method Header / Method Declaration Sum of an Array: Sum of an Array int sumOfArray ( int arr []) { int sum=0; for( int x:arr) { sum= sum+x ; } return sum; } Taking an integer array and returning single value of int data type Average of an Array: Average of an Array float averageOfArray ( int arr []) { int sum=0; float avg ; for( int x:arr) { sum= sum+x ; } avg =(float)sum/ arr.length ; return avg ; } Maximum of an Array: Maximum of an Array byte maximumOfArray (byte arr []) { byte max= Byte.MIN_VALUE ; for(byte x:arr) { if(x>max) { max=x; } } return max; } Minimum value of byte is -128. Minimum of an Array: Minimum of an Array byte minimumOfArray (byte arr []) { byte min= Byte.MAX_VALUE ; for(byte x:arr) { if(x<min) { min=x; } } return min; } Maximum value of byte is 127. Wrapper class for byte data type Return Array from Called Method: Return Array from Called Method Return prime numbers between 1 and 100: Return prime numbers between 1 and 100 int [] getPrime1To100 () { int arr [] = new int [100]; for( int i=1,j=1; i <=100;i++) { if( isPrime (i ) ==true) { arr [j]=i; j++; } } return arr ; } Taking no parameters but returning an array. A method cannot return multiple values but it can return an array. Complete Program: Complete Program public class function1 { static int [] getPrime1To100 () { int arr [] = new int [100]; for( int i=1,j=1; i<=100;i++) { if( isPrime (i)==true) { arr [j]=i; j++; } } return arr ; } public static void main(String args []) { int art []=getPrime1To100 (); for( int x:art) { if(x !=0) { System.out.println (x ); } } }//end of main method }//end of public class Array contains 100 values, some are prime numbers other are default values (0). Reverse array: Reverse array byte[] reverseArray (byte arr []) { byte xyz[]=new byte[100]; int i=arr.length-1; for(j=0; i >=0 ; i-- , j ++) { xyz[i ]= arr [j]; } return xyz; } Returning byte array to calling method 5 78 89 1655 Original Array 1655 89 78 5 Converted Array This method takes an array(multiple byte type values) and returns an array(multiple byte type values). Reverse digits of all array elements 1: Reverse digits of all array elements 1 Example Original Array Converted Array 5 78 89 1655 464 782 346 75623 5 87 98 5561 464 287 643 32657 Reverse digits of all array elements 2: Reverse digits of all array elements 2 void reverseEveryArrayElement ( int a[]) { for( int i=0;i< a.length;i ++) { a[i ]= reverseNumber (a[i]); } } This method is modifying original array elements. Replacing every element of array with its reverse number Pass by Reference nce E xample Complete Program: Complete Program public static void main(String args []) { int a []={5,78,89,1655,464,782,346,75623}; reverseEveryArrayElement (a); arrayTraversing (a); } static void reverseEveryArrayElement ( int a[]) { for( int i=0;i< a.length;i ++) { a[i ]= reverseNumber (a[i]); } } Advantages of Using Methods: Advantages of Using Methods To help make the program more understandable To modularize the tasks of the program building blocks of the program Write a module once those lines of source code are called multiple times in the program 49 Advantages of Using Methods: Advantages of Using Methods While working on one function, you can focus on just that part of the program construct it, debug it, perfect it. 5. Different people can work on different functions simultaneously. 6. If a function is needed in more than one place in a program, or in different programs, you can write it once and use it many times 50 PowerPoint Presentation: Thank You

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