40+ examples of user defined methods in java with explanation
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40+ examples of user defined methods in java with explanation

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40+ examples of user defined methods in java with explanation, ...

40+ examples of user defined methods in java with explanation,
advantages,
terms,
exercises,
pass arrays to methods,
return array from methods,
for each loop examples,
build complex programs using your defined methods
animation included

INDEX

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

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
Decimal to binary, octal, hex
Binary to decimal, octal, hex
Octal to binary,decimal, hex
Hexadecimal to binary, octal, decimal

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40+ examples of user defined methods in java with explanation 40+ examples of user defined methods in java with explanation Presentation Transcript

  • User Defined Methods in Java With Animation
  • Index 1. 2. Advantages Simple Programs using Methods a) b) c) d) e) f) g) h) i) j) k) l) m) n) o) p) q) r) 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 3. Pass Array to Methods a) b) c) d) e) 4. 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 a) b) Reverse array Reverse every element of an array
  • Function v/s Method View slide
  • Function v/s Method Q.)What is the difference between a function and a method.? View slide
  • 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.
  • 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) void display() { System.out.println("this is inside method body"); }
  • Function with no arguments and no return(no input no output) void display() { System.out.println("this is inside method body"); } When you want to return no value, then set return type to void
  • Function with no arguments and no return(no input no output) Name of the function is “display” void display() { System.out.println("this is inside method body"); } When you want to return no value, then set return type to void
  • Function with no arguments and no return(no input no output) Name of the function is “display” No arguments here void display() { System.out.println("this is inside method body"); } When you want to return no value, then set return type to void
  • 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 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 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 Calling
  • Add two integer numbers int add(int a, int b) { int c=a+b; return c; }
  • Add two integer numbers int add(int a, int b) { int c=a+b; return c; } Two Integer Arguments
  • Add two integer numbers int add(int a, int b) { int c=a+b; return c; } Returning integer value to calling method Two Integer Arguments
  • 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 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 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)); } } main method is calling method, because it is calling display method.
  • Average of three integer numbers double { double d; d=((double)a+b+c)/3; return d; } )
  • Average of three integer numbers double { double d; d=((double)a+b+c)/3; return d; } ) This method takes multiple arguments and returns single value
  • Average of three integer numbers double { double d; d=((double)a+b+c)/3; return d; } ) This method takes multiple arguments and returns single value
  • Calculate circle Area double { double area=Math.PI*radius*radius; return area; }
  • Calculate circle Area double { double area=Math.PI*radius*radius; return area; }
  • Convert Fahrenheit to Celsius double convertFahToCel(double fah) { double cel=(fah-32)*5/9; return cel; }
  • Convert Fahrenheit to Celsius double convertFahToCel(double fah) { double cel=(fah-32)*5/9; return cel; } This method takes one argument and returns single value
  • Check number is even or not boolean checkEven(int n) { if(n%2==0) { return true; } else { return false; } }
  • 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 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 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 boolean isPalindrome(int n) { int rev = if(n==rev) { return true; } else { return false; } FOCUS ON ONE WORK } We need to focus on palindrome not on reverse number code, this is a advantage of method. ;
  • Check number is palindrome or not boolean isPalindrome(int n) { int rev = if(n==rev) { return true; } else { return false; } FOCUS ON ONE WORK } We need to focus on palindrome not on reverse number code, this is a advantage of method. ; Using previous slide’s reverse number method
  • Count number of digits in a number This is Exercise
  • Sum of digits This is Exercise
  • 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 long getLCM(int n1,int n2,int n3) { long result1 = getLCM(n1,n2); long finalResult=getLCM((int) result1,n3); return finalResult; }
  • 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
  • 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; }
  • 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; } 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; }
  • 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; } Narrowing type conversion
  • 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; }
  • 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; }
  • 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
  • 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; }
  • 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; } 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; }
  • 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; } Narrowing type conversion
  • 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; }
  • 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; }
  • 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
  • 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; }
  • 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; } User Defined getLCM() method
  • Print prime numbers between 1 and 100 void printPrime1To100() { for(int i=1;i<=100;i++) { if( ==true) { System.out.println(i); } } User } defined method
  • Print prime numbers between 200 and 500 which are Palindrome numbers too This is exercise
  • 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 String convertDecimalToBinary(long n) { int base=2; String ans=convertDecimalToXXX(n,base); return ans; }
  • Convert Decimal to Octal String convertDecimalToOctal(long n) { int octal_base=8; String ans=convertDecimalToXXX(n,octal_base); return ans; }
  • Convert Decimal to Hexadecimal String convertDecimalToHexadecimal(long n) { int hex_base=16; String ans=convertDecimalToXXX(n,hex_base); return ans; }
  • 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 long convertBinaryToDecimal(String binary_number) { int binary_base=2; long ans=convertXXXToDecimal(binary_base,binary_number); return ans; }
  • Convert Octal to Decimal long convertOctalToDecimal(String binary_number) { int binary_base=8; long ans=convertXXXToDecimal(binary_base,binary_number); return ans; }
  • Convert Hexadecimal to Decimal long convertHexToDecimal(String binary_number) { int binary_base=2; long ans=convertXXXToDecimal(binary_base,binary_number); return ans; }
  • Convert Hexadecimal to Octal String convertHexToOctal(String hexNumber) { long decimal=convertHexToDecimal(hexNumber); String ans=convertDecimalToOctal(decimal); return ans; }
  • Convert Hexadecimal to Binary String convertHexToBinary(String hexNumber) { long decimal=convertHexToDecimal(hexNumber); String ans=convertDecimalToBinary(decimal); return ans; }
  • Convert Octal to Hexadecimal String convertOctalToHex(String octalNumber) { long decimal=convertOctalToDecimal(octalNumber); String ans=convertDecimalToHex(decimal); return ans; }
  • Convert Octal to Binary String convertOctalToBinary(String octalNumber) { long decimal=convertOctalToDecimal(octalNumber); String ans=convertDecimalToBinary(decimal); return ans; }
  • Print All elements of an Array void arrayTraversing(int arr[]) { for(int x:arr) { System.out.println(x); } }
  • Print All elements of an Array void arrayTraversing(int arr[]) { for(int x:arr) { System.out.println(x); } }
  • Print All elements of an Array Method Header / Method Declaration void arrayTraversing(int arr[]) { for(int x:arr) { System.out.println(x); } }
  • Sum of an Array int sumOfArray(int arr[]) { int sum=0; for(int x:arr) { sum=sum+x; } return sum; }
  • Sum of an Array int sumOfArray(int arr[]) { int sum=0; for(int x:arr) { sum=sum+x; Taking an integer array and returning } single value of int data type return sum; }
  • 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 byte maximumOfArray(byte arr[]) { byte max=Byte.MIN_VALUE; for(byte x:arr) { if(x>max) { max=x; } } return max; }
  • 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 of an Array byte minimumOfArray(byte arr[]) { byte min=Byte.MAX_VALUE; for(byte x:arr) { if(x<min) { min=x; } } return min; }
  • Minimum of an Array byte minimumOfArray(byte arr[]) { byte min=Byte.MAX_VALUE; for(byte x:arr) { if(x<min) { min=x; } } return min; } Wrapper class for byte data type
  • 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 prime numbers between 1 and 100 A method cannot int[] getPrime1To100() return multiple { values but it can int arr[] = new int[100]; return an array. for(int i=1,j=1; i<=100;i++) { if( ==true) { arr[j]=i; j++; } } Taking no parameters but return arr; returning an array. }
  • 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 byte[] reverseArray(byte arr[]) { Returning byte array to calling method byte xyz[]=new byte[100]; int i=arr.length-1; for(j=0; i>=0; i-- , j++) { This method takes an xyz[i]=arr[j]; array(multiple byte } type values) and returns an return xyz; array(multiple byte } type values).
  • Original Array 5 78 Reverse array 89 1655 byte[] reverseArray(byte arr[]) { Returning byte array to calling method byte xyz[]=new byte[100]; int i=arr.length-1; for(j=0; i>=0; i-- , j++) { This method takes an xyz[i]=arr[j]; array(multiple byte } type values) and returns an return xyz; array(multiple byte } type values).
  • Original Array 5 78 Reverse array 89 1655 1655 Converted Array 89 78 5 byte[] reverseArray(byte arr[]) { Returning byte array to calling method byte xyz[]=new byte[100]; int i=arr.length-1; for(j=0; i>=0; i-- , j++) { This method takes an xyz[i]=arr[j]; array(multiple byte } type values) and returns an return xyz; array(multiple byte } type values).
  • Original Array 5 78 Reverse array 89 1655 1655 Converted Array 89 78 5 byte[] reverseArray(byte arr[]) { Returning byte array to calling method byte xyz[]=new byte[100]; int i=arr.length-1; for(j=0; i>=0; i-- , j++) { This method takes an xyz[i]=arr[j]; array(multiple byte } type values) and returns an return xyz; array(multiple byte } type values).
  • Reverse digits of all array elements 1 Example Original Array 5 78 89 1655 464 782 346 75623 98 5561 464 287 643 32657 Converted Array 5 87
  • Reverse digits of all array elements 2 void reverseEveryArrayElement(int a[]) { for(int i=0;i<a.length;i++) { a[i]=reverseNumber(a[i]); } }
  • Reverse digits of all array elements 2 void reverseEveryArrayElement(int a[]) { for(int i=0;i<a.length;i++) { a[i]=reverseNumber(a[i]); } } Replacing every element of array with its reverse number
  • Reverse digits of all array elements 2 void reverseEveryArrayElement(int a[]) { for(int i=0;i<a.length;i++) { a[i]=reverseNumber(a[i]); } } Replacing every element of array with its reverse number This method is modifying original array elements.
  • 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    48
  • Advantages of Using Methods 1. To help make the program more understandable   48
  • Advantages of Using Methods 1. To help make the program more understandable 2. To modularize the tasks of the program – building blocks of the program  48
  • Advantages of Using Methods 1. To help make the program more understandable 2. To modularize the tasks of the program – building blocks of the program 3. Write a module once – those lines of source code are called multiple times in the program 48
  • Advantages of Using Methods    49
  • Advantages of Using Methods 4. While working on one function, you can focus on just that part of the program – – – construct it, debug it, perfect it.   49
  • Advantages of Using Methods 4. 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.  49
  • Advantages of Using Methods 4. 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 49