use of setter and getter methods

Hi,

Following is a code snippet that teaches java coding conventions.
Around the bottom of the snippet, I notice setter and getter methods.
I don't know why I am advised to write setter and getter method. Could
anyone explain what the use of setter and getter methods are.

Thank you.

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// Non javadoc comments, authorship, and
// class development history.

package javatech.xxx.yyy.zzz;

import java.io.*;

/** javadoc comments about the class. **/
public class SomeClassName
{
  int fInstanceVal = 1;
  double fVal = 0;
  Integer fInstanceRef;

public SomeClassName {
   ... constructor code ...
} // ctor - for longer constructors

/** Describe the method. **/
  public void methodName (...) {
    int x = 5;
    some_method (x);
    if (test) {
      do_something ();
    }
    else {
      ...
    }
    ...
    try {
      xxx ();
    }
    catch (Exception e) {
      handle_it ();
    }
  } // methodName - for longer methods

  /** Longer comment.
   * - this asterisk is ignored by javadoc
   **/
  public void someMethodWithLotsOfParameters (
    int param1,
    int param2,
    etc.
  ) throws SomeException {
    ...
  } // someMethodWithLotsOfParameters

  /** Private method names with underscores. **/
  private void some_method (int i) {
    ...
  } // some_method

  /** Getter method. **/
  double getVal () {
    return fVal;
  }

  /** Setter method. **/
  void setVel (double val) {
    fVal = val;
  }

} // class SomeClassName