Java - Read For Learn

What is the “continue” keyword and how does it work in Java?

A continue statement without a label will re-execute from the condition the innermost while or do loop, and from the update expression of the innermost for loop. It is often used to early-terminate a loop’s processing and thereby avoid deeply-nested if statements. In the following example continue will get the next line, without processing the following statement in the loop. With a label, continue will re-execute from the loop … Read more

What is a JavaBean exactly?

A JavaBean is just a standard All properties are private (use getters/setters) A public no-argument constructor Implements Serializable. That’s it. It’s just a convention. Lots of libraries depend on it though. With respect to Serializable, from the API documentation: Serializability of a class is enabled by the class implementing the java.io.Serializable interface. Classes that do not implement this interface will not … Read more

Converting double to string

This will convert double to String

Could not reserve enough space for object heap

Run the JVM with -XX:MaxHeapSize=512m (or any big number as you need) (or -Xmx512m for short)

Is Java “pass-by-reference” or “pass-by-value”?

Java is always pass-by-value. Unfortunately, when we deal with objects we are really dealing with object-handles called references which are passed-by-value as well. This terminology and semantics easily confuse many beginners. It goes like this: In the example above aDog.getName() will still return “Max”. The value aDog within main is not changed in the function foo with the Dog “Fifi” as the object reference is passed by value. If it … Read more

Exception in thread “main” java.util.NoSuchElementException

You close the second Scanner which closes the underlying InputStream, therefore the first Scanner can no longer read from the same InputStream and a NoSuchElementException results. The solution: For console apps, use a single Scanner to read from System.in. Aside: As stated already, be aware that Scanner#nextInt does not consume newline characters. Ensure that these are consumed before attempting to call nextLine again by using Scanner#newLine(). See: Do not create multiple buffered wrappers on … Read more

Convert String to double in Java

You can use Double.parseDouble() to convert a String to a double: For your case it looks like you want:

What does “Could not find or load main class” mean?

The java <class-name> command syntax First of all, you need to understand the correct way to launch a program using the java (or javaw) command. The normal syntax1 is this: where <option> is a command line option (starting with a “-” character), <class-name> is a fully qualified Java class name, and <arg> is an arbitrary … Read more

Java String Split by “|”

ou must use: This is because the split method takes a regular expression, and | is one of the special characters. It means ‘or’. That means you are splitting by ” or ”, which is just ”. Therefore it will split between every character. You need two slashes because the first one is for escaping the actual \ in the string, since \ is Java’s escape … Read more

Sort an array in Java

Loops are also very useful to learn about, esp When using arrays,

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