title: error: bad operand types for binary operator '=='
body: <p>Just wanted to do a task in my Book but I don't get why this is wrong.It should say that negative Numbers aren't positive and positive aren0t negative with a Boolean.
  This is my Code:</p>
  
  <pre><code>import javax.swing.JOptionPane;
  
  public class Zahlentest {
      public static void main(String[] args) {
  
          String eingabe;
          char Zahl;
          boolean istVokal;
          eingabe = JOptionPane.showInputDialog("Geben Sie eine Zahl ein: ");
          if (Zahl == "- &amp;&amp; Zahl") {
              istVokal = false;
          } else {
              istVokal = true;
          }
          if (istVokal == true) {
              JOptionPane.showMessageDialog(null, "Die Zahl ist nicht negativ!");
          } else {
              JOptionPane.showMessageDialog(null, "Die Zahl ist negativ!");
          }
      }
  }
  </code></pre>
  
  <p>I don't know what I am doing wrong ... pls help.
  This is error code:</p>
  
  <pre><code>Zahlentest.java:10: error: bad operand types for binary operator '=='
              if (Zahl == "- &amp;&amp; Zahl") {
               ^
        first type:  char
        second type: String
      1 error
  </code></pre>