Default values for primitives and references : Data Type Introduction « Data Type « Java Tutorial

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2. Data Type
3. Data Type Introduction

public class ClassInitializer1 {
  static boolean bool;
  static byte by;
  static char ch;
  static double d;
  static float f;
  static int i;
  static long l;
  static short sh;
  static String str;

  public static void main(String[] args) {
    System.out.println("bool = " + bool);
    System.out.println("by = " + by);
    System.out.println("ch = " + ch);
    System.out.println("d = " + d);
    System.out.println("f = " + f);
    System.out.println("i = " + i);
    System.out.println("l = " + l);
    System.out.println("sh = " + sh);
    System.out.println("str = " + str);
  }
}