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Java methods

Java methods tutorial: Java program consists of one or more classes, and a class may contain method(s). A class can do very little without methods. In this tutorial, we learn about Java methods (known as functions in C and C++ programming languages). A method has a name and return type. The main method is a must in a Java program as execution begins from it.

Syntax of methods

"Access specifier" "Keyword(s)" "return type" methodName(List of arguments) {
// Body of method
}

Access specifiers can be public or private, which decides whether other classes can call a method.
Keywords such as static or synchronized are used for some particular methods.
Return type indicates return value, which method returns.
Method name is a valid Java identifier name.

Access specifiers, keywords, and arguments are optional.

Examples of methods declaration:
public static void main(String[] args);
void myMethod();
private int maximum();
public synchronized int search(java.lang.Object);

Java Method example program

class Methods {
   
  // Constructor method
 
  Methods() {
    System.out.println("Constructor method is called when an object of its class is created");
  }
 
  // Main method where program execution begins
 
  public static void main(String[] args) {
    staticMethod();
    Methods object = new Methods();
    object.nonStaticMethod();
  }
 
  // Static method
 
  static void staticMethod() {
    System.out.println("Static method can be called without creating object");
  }
 
  // Non static method
 
  void nonStaticMethod() {
    System.out.println("Non static method must be called by creating an object");
  }
}

Output of program:
Java methods program output

Download Methods program class file.

Java methods list

Java has a built-in library of many useful classes, and there are thousands of methods that we can use in a program. Just call a method and get your work done :). You can find the list of methods in a class by typing following command on command prompt:

javap package.classname

For example
javap java.lang.String // list all methods and constants of String class.
javap java.math.BigInteger // list constants and methods of BigInteger class in java.math package

Java String methods

String class contains methods that are useful for performing operations on String(s). The below program illustrate how to use inbuilt methods of String class.

Java string class program

class StringMethods
{
  public static void main(String args[])
  {
    int n;
    String s = "Java programming", t = "", u = "";
   
    System.out.println(s);
   
    // Find the length of string
   
    n = s.length();
    System.out.println("Number of characters = " + n);
   
    // Replace characters in the string
   
    t = s.replace("Java", "C++");
    System.out.println(s);
    System.out.println(t);
   
    // Concatenating string with another string
   
    u = s.concat(" is fun");
    System.out.println(s);
    System.out.println(u);
  }
}

Output of program:
Java string methods program