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Principios Básicos de Java
course content

Contenido del Curso

Principios Básicos de Java

Principios Básicos de Java

1. Iniciando
Desarrollo BackendRol de Java en el BackendVentajas de JavaTipos de Memoria en JavaSintaxis de JavaTu Primer ProgramaComentarios
2. Tipos Básicos, Operaciones
Tipos de Datos PrimitivosDesafíoTabla de Caracteres y ASCIIOperaciones Matemáticas en JavaSentencia If-ElseSentencia Switch-CaseDesafío
3. Loops
Introducción A Los LoopsLoop WhileLoop Do-WhileChallenge: Building a Server Retry MechanismLoop ForIncremento Y DecrementoLoop Infinito (bonus)Desafío: Factorial
4. Arrays
¿Qué es Array?Usando Loops con ArraysIndex Out Of BoundsArray BidimensionalIteración en una Array BidimensionalLoop For-Each
5. String
¿Qué Es String?Métodos Básicos En String Parte 1Métodos Básicos en String Parte 2DesafíoNullPointer ExceptionStringBuilderConjunto de Strings, Método Equals()Resumen

book
NullPointer Exception

NPE

NullPointerException or NPE is an error every Java programmer is familiar with. This error holds the record for irritating programmers.

First, let's understand the concept of the null value for a string variable. When we create a string variable but forget to initialize, it acquires a null value. In comparison, if we don't initialize an int variable, it acquires a value of 0.

Let's consider an example of a string variable with a null value:

java

Main

copy

              
12345678

            
package com.example;

public class Main {
    public static void main(String[] args) {
        String string = null;
        System.out.println(string);
    }
}

As you can see, the output on the screen is null, and the code seems to be working. But let's now try using any method with a variable with the null value:

java

Main

copy

              
123456789

            
package com.example;

public class Main {
    public static void main(String[] args) {
        String string = null;
        string.toLowerCase();
        System.out.println(string);
    }
}

When attempting to call any method on a string variable with a null value, we receive a NullPointerException.

You might think this error is not so serious, but later, when you receive values not written by you personally, you may often come across it. Therefore, it is crucial to understand how to resolve this error now.

Ways to avoid NPE:

  • Be attentive. If you create a string variable, double-check if you have initialized it;
  • Use a null check before using the variable, for example:
java

Main

copy

              
123456789101112

            
package com.example;

public class Main {
    public static void main(String[] args) {
        String string = null;
        if (string == null) { //null check
            System.out.println("Can't use methods with string, because value is null");
        } else {
            System.out.println(string);
        }
    }
}
Tarea
test

Swipe to begin your solution

I have a string array, and I'm trying to print it using a for-each loop, but I keep encountering an error that's already bothering me. Resolve this issue so that the data from my array will be displayed on the screen.

Solución

java

solution

Switch to desktopCambia al escritorio para practicar en el mundo realContinúe desde donde se encuentra utilizando una de las siguientes opciones
¿Todo estuvo claro?

¿Cómo podemos mejorarlo?

¡Gracias por tus comentarios!

Sección 5. Capítulo 5
toggle bottom row

book
NullPointer Exception

NPE

NullPointerException or NPE is an error every Java programmer is familiar with. This error holds the record for irritating programmers.

First, let's understand the concept of the null value for a string variable. When we create a string variable but forget to initialize, it acquires a null value. In comparison, if we don't initialize an int variable, it acquires a value of 0.

Let's consider an example of a string variable with a null value:

java

Main

copy

              
12345678

            
package com.example;

public class Main {
    public static void main(String[] args) {
        String string = null;
        System.out.println(string);
    }
}

As you can see, the output on the screen is null, and the code seems to be working. But let's now try using any method with a variable with the null value:

java

Main

copy

              
123456789

            
package com.example;

public class Main {
    public static void main(String[] args) {
        String string = null;
        string.toLowerCase();
        System.out.println(string);
    }
}

When attempting to call any method on a string variable with a null value, we receive a NullPointerException.

You might think this error is not so serious, but later, when you receive values not written by you personally, you may often come across it. Therefore, it is crucial to understand how to resolve this error now.

Ways to avoid NPE:

  • Be attentive. If you create a string variable, double-check if you have initialized it;
  • Use a null check before using the variable, for example:
java

Main

copy

              
123456789101112

            
package com.example;

public class Main {
    public static void main(String[] args) {
        String string = null;
        if (string == null) { //null check
            System.out.println("Can't use methods with string, because value is null");
        } else {
            System.out.println(string);
        }
    }
}
Tarea
test

Swipe to begin your solution

I have a string array, and I'm trying to print it using a for-each loop, but I keep encountering an error that's already bothering me. Resolve this issue so that the data from my array will be displayed on the screen.

Solución

java

solution

Switch to desktopCambia al escritorio para practicar en el mundo realContinúe desde donde se encuentra utilizando una de las siguientes opciones
¿Todo estuvo claro?

¿Cómo podemos mejorarlo?

¡Gracias por tus comentarios!

Sección 5. Capítulo 5
Switch to desktopCambia al escritorio para practicar en el mundo realContinúe desde donde se encuentra utilizando una de las siguientes opciones
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