// Fig. 7.11: LinearSearch.java
// Linear search of an array.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class LinearSearch extends JApplet implements ActionListener {

   JLabel enterLabel, resultLabel;
   JTextField enterField, resultField;
   int array[];

   // set up applet's GUI
   public void init()
   {
      // get content pane and set its layout to FlowLayout
      Container container = getContentPane();
      container.setLayout( new FlowLayout() );

      // set up JLabel and JTextField for user input
      enterLabel = new JLabel( "Enter integer search key" );
      container.add( enterLabel );

      enterField = new JTextField( 10 );
      container.add( enterField );

      // register this applet as enterField's action listener
      enterField.addActionListener( this );

      // set up JLabel and JTextField for displaying results
      resultLabel = new JLabel( "Result" );
      container.add( resultLabel );

      resultField = new JTextField( 20 );
      resultField.setEditable( false );
      container.add( resultField );

      // create array and populate with even integers 0 to 198
      array = new int[ 100 ];

      for ( int counter = 0; counter < array.length; counter++ )
         array[ counter ] = 2 * counter;

   } // end method init

   // search array for specified key value
   public int linearSearch( int array2[], int key ) 
   {   
      // loop through array elements
      for ( int counter = 0; counter < array2.length; counter++ )

         // if array element equals key value, return location
         if ( array2[ counter ] == key )
            return counter;

      return -1;  // key not found

   } // end method linearSearch

   // obtain user input and call method linearSearch
   public void actionPerformed( ActionEvent actionEvent )
   {
      // input also can be obtained with enterField.getText()
      String searchKey = actionEvent.getActionCommand();

      // pass array reference to linearSearch; normally, a reference to an
      // array is passed to a method to search corresponding array object
      int element = linearSearch( array, Integer.parseInt( searchKey ) );

      // display search result
      if ( element != -1 )
         resultField.setText( "Found value in element " + element );
      else
         resultField.setText( "Value not found" );

   } // method actionPerformed

} // end class LinearSearch


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