Why will you use Comparator and Comparable interfaces?

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java.util.Comparator
java.util.Comparator compares some other class’s instances.

java.lang.Comparable
java.lang.Comparable compares another object with itself.

Differentiate between final, finally and finalize.

The keyword is final. It is used for declaring a constant It prevents a class from producing subclasses.

finally is a code.It always executes when the try block is finished, Unless System.exit() has been called.finalize() is a method, Before discarding by the garbage collector it is invoked.

Differentiate JAR and WAR files

JAR files:

  • JAR files is the acronym stands for Java ARchive fles.
  • JAR files allow aggregating many files into one,
  • JAR is usually used to hold Java classes in a library.

WAR files:

  • WAR files is the acronym stands for Web ARchive fles.
  • WAR stores XML, java classes, and JavaServer pages
  • WAR is mainly used for Web Application purposes.

In a Java , how can you send program messages on the system console, but error messages, to a file?

The class System has a variable out that denotes the standard output.

The standard error device represents the variable err .

Naturally, they both point at the system console.

 

In this way, the standard output can be sent to the file:

Stream x = new Stream(new FileOutputStream(“error.txt”));

System.setErr(x);

System.Out(x);