ch05 revisions

Author: ChrisMayfield

ch05/ChainNest.java

@@ -0,0 +1,25 @@
+public class ChainNest {
+
+    public static void main(String[] args) {
+        int x = 0;
+
+        if (x > 0) {
+            System.out.println("x is positive");
+        } else if (x < 0) {
+            System.out.println("x is negative");
+        } else {
+            System.out.println("x is zero");
+        }
+
+        if (x > 0) {
+            System.out.println("x is positive");
+        } else {
+            if (x < 0) {
+                System.out.println("x is negative");
+            } else {
+                System.out.println("x is zero");
+            }
+        }
+    }
+
+}

ch05/Conditional.java

@@ -0,0 +1,27 @@
+public class DigitUtil {
+
+    public static boolean isSingleDigit(int x) {
+        if (x > -10 && x < 10) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    public static boolean isSingleDigit2(int x) {
+        return x > -10 && x < 10;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(isSingleDigit(2));
+        boolean bigFlag = !isSingleDigit(17);
+
+        int z = 9;
+        if (isSingleDigit(z)) {
+            System.out.println("z is small");
+        } else {
+            System.out.println("z is big");
+        }
+    }
+
+}

ch05/DigitUtil.java

@@ -0,0 +1,32 @@
+public class IfElse {
+
+    public static void main(String[] args) {
+        int x = 17;
+        int n = 18;
+
+        if (x > 0) {
+            System.out.println("x is positive");
+        }
+
+        if (x % 2 == 0) {
+            System.out.println("x is even");
+        } else {
+            System.out.println("x is odd");
+        }
+
+        // look, no braces...bad idea!
+        if (x % 2 == 0)
+            System.out.println("x is even");
+        else
+            System.out.println("x is odd");
+
+        if (x > 0)
+            System.out.println("x is positive");
+            System.out.println("x is not zero");
+
+        if (x % 2 == 0); { // incorrect semicolon
+            System.out.println("x is even");
+        }
+    }
+
+}

ch05/IfElse.java

@@ -20,7 +20,7 @@ public static void main(String[] args) {
 
         // check the range
         double x = in.nextDouble();
-        if (x >= 0) {
+        if (x > 0) {
             double y = Math.log(x);
             System.out.println("The log is " + y);
         } else {

ch05/Logarithm.java

@@ -0,0 +1,56 @@
+public class LogicalOpers {
+
+    public static void main(String[] args) {
+        int x = 0;
+        int y = 0;
+
+        // nested
+        if (x == 0) {
+            if (y == 0) {
+                System.out.println("Both x and y are zero");
+            }
+        }
+
+        // combined
+        if (x == 0 && y == 0) {
+            System.out.println("Both x and y are zero");
+        }
+
+        // chained
+        if (x == 0) {
+            System.out.println("Either x or y is zero");
+        } else if (y == 0) {
+            System.out.println("Either x or y is zero");
+        }
+
+        // combined
+        if (x == 0 || y == 0) {
+            System.out.println("Either x or y is zero");
+        }
+
+        // De Morgan's
+        if (!(x == 0 || y == 0)) {
+            System.out.println("Neither x nor y is zero");
+        }
+        if (x != 0 && y != 0) {
+            System.out.println("Neither x nor y is zero");
+        }
+
+        // boolean variables
+        boolean flag;
+        flag = true;
+        boolean testResult = false;
+
+        boolean evenFlag = (x % 2 == 0);    // true if x is even
+        boolean positiveFlag = (x > 0);     // true if x is positive
+
+        if (evenFlag) {
+            System.out.println("n was even when I checked it");
+        }
+
+        if (!evenFlag) {
+            System.out.println("n was odd when I checked it");
+        }
+    }
+
+}

ch05/LogicalOpers.java

@@ -0,0 +1,56 @@
+public class Switch {
+
+    public static void main(String[] args) {
+        int number = 0;
+        String word;
+
+        // if-else-if
+
+        if (number == 1) {
+            word = "one";
+        } else if (number == 2) {
+            word = "two";
+        } else if (number == 3) {
+            word = "three";
+        } else {
+            word = "unknown";
+        }
+
+        // same result as above
+
+        switch (number) {
+            case 1:
+                word = "one";
+                break;
+            case 2:
+                word = "two";
+                break;
+            case 3:
+                word = "three";
+                break;
+            default:
+                word = "unknown";
+                break;
+        }
+
+        System.out.print(number);
+        System.out.print(word);
+
+        // switch blocks fall through
+
+        String food = "apple";
+        switch (food) {
+            case "apple":
+            case "banana":
+            case "cherry":
+                System.out.println("Fruit!");
+                break;
+            case "asparagus":
+            case "broccoli":
+            case "carrot":
+                System.out.println("Vegetable!");
+                break;
+        }
+    }
+
+}