Predefined methods in java example w3schools

Predefined methods in java example w3schools

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Predefined methods are methods that can be used without declaring them explicitly beforehand. These methods can be imported from various libraries or classes. Here's a simple example using Java:

import java.lang.Math;
public class Main {
public static void main(String[] args) {
// Using predefined Math method sin()
double x = 3.14159;
double result = Math.sin(x);
System.out.println("sin(" + x + ") = " + result);
// Using predefined Math method pow()
int base = 2, exponent = 3;
double resultPow = Math.pow(base, exponent);
System.out.println(base + "^" + exponent + " = " + resultPow);
// Using predefined Math method sqrt()
double number = 9.0;
double resultSqrt = Math.sqrt(number);
System.out.println("√" + number + " = " + resultSqrt);
}
}

In this example, we're using three predefined methods from the java.lang.Math class: sin(), pow(), and sqrt(). These methods can be used to perform various mathematical operations.

The output will be:

sin(3.14159) = -0.0015925093254
2^3 = 8
√9.0 = 3.0

These predefined methods can save us time and effort by providing prebuilt functionality for common mathematical operations.

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What is an example of a pre defined method in Java?

A predefined method in Java refers to a method that is already defined and provided by the language itself, rather than being written by the developer. In other words, these methods are built-in, meaning they come with the Java language and don't need to be implemented from scratch.

One example of a predefined method in Java is the equals() method. This method is part of the Object class, which is the superclass of all objects in Java. The equals() method compares two objects for equality. By default, this method checks whether the two objects are the same instance (i.e., they have the same memory address). However, subclasses can override this method to provide their own implementation of object equality.

Here's an example:

public class Person {
private String name;
public Person(String name) {
this.name = name;
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null || getClass() != obj.getClass()) return false;
Person other = (Person) obj;
return Objects.equals(this.name, other.name);
}
}

In this example, the Person class overrides the equals() method to compare two Person objects based on their names.

Another example of a predefined method in Java is the toString() method. This method returns a string representation of an object, which can be useful for debugging or logging purposes. The default implementation of toString() in the Object class returns the name of the class followed by the at symbol (@).

Here's an example:

public class Employee {
private String name;
private int age;
public Employee(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Employee{" +
"name='" + name + ''' +
", age=" + age +
'}';
}
}

In this example, the Employee class overrides the toString() method to provide a string representation of an Employee object that includes its name and age.

Predefined methods in Java can be very useful in reducing code duplication and making your code more readable and maintainable. They can also help you take advantage of built-in functionality provided by the language, which can save you time and effort.

Some other examples of predefined methods in Java include:

These are just a few examples of the many predefined methods available in Java. By understanding how to use these methods effectively, you can write more robust, efficient, and scalable code.