fixed last method

src/main/java/ru/ifellow/JSchool/introdution/FirstSteps.java

@@ -2,88 +2,185 @@
 
 public class FirstSteps {
 
-    public int sum (int x, int y){
-
-    }
-
-    public int mul (int x, int y){
-
+    public int sum(int x, int y) {
+        return x + y;
     }
 
-    public int div (int x, int y){
-
+    public int mul(int x, int y) {
+        return x * y;
     }
 
-    public int mod (int x, int y){
-
+    public int div(int x, int y) {
+        return x / y;
     }
 
-    public boolean isEqual (int x, int y){
-
+    public int mod(int x, int y) {
+        return x % y;
     }
 
-    public boolean isGreater (int x, int y){
-
+    public boolean isEqual(int x, int y) {
+        return x == y;
     }
 
-    public boolean isInsideRect(int xLeft, int yTop, int xRight, int yBottom, int x, int y){
-
+    public boolean isGreater(int x, int y) {
+        return x > y;
     }
 
-    public int sum(int[] array){
-
+    public boolean isInsideRect(int xLeft, int yTop, int xRight, int yBottom, int x, int y) {
+        return x >= xLeft && x <= xRight && y <= yTop && y >= yBottom;
     }
 
-    public int mul(int[] array){
-
-    }
-
-    public int min(int[] array){
-
-    }
-
-    public int max(int[] array){
-
-    }
-
-    public double average(int[] array){
-
-    }
-
-    public boolean isSortedDescendant(int[] array){
-
+    public int sum(int[] array) {
+        int sum = 0;
+        if (array != null) {
+            for (int i : array) {
+                sum = sum(sum, i);
+            }
+        }
+        return sum;
     }
 
-    public void cube(int[]array){
-
-    }
-
-    public boolean find(int[]array, int value){
-
-    }
-
-    public void reverse(int[]array){
-
-    }
-
-    public boolean isPalindrome(int[]array){
-
-    }
-
-    public int sum(int[][] matrix){
-
-    }
-
-    public int max(int[][] matrix){
-
-    }
-
-    public int diagonalMax(int[][] matrix){
-
-    }
-
-    public boolean isSortedDescendant(int[][] matrix){
-
+    public int mul(int[] array) {
+        int mul = 0;
+        if (array != null && array.length > 0) {
+            mul = array[0];
+            for (int i = 1; i < array.length; i++) {
+                mul = mul(mul, array[i]);
+            }
+        }
+        return mul;
+    }
+
+    public int min(int[] array) {
+        int min = Integer.MAX_VALUE;
+        if (array != null) {
+            for (int i : array) {
+                if (isGreater(min, i)) {
+                    min = i;
+                }
+            }
+        }
+        return min;
+    }
+
+    public int max(int[] array) {
+        int max = Integer.MIN_VALUE;
+        if (array != null) {
+            for (int i : array) {
+                if (isGreater(i, max)) {
+                    max = i;
+                }
+            }
+        }
+        return max;
+    }
+
+    public double average(int[] array) {
+        double avg = 0;
+        if (array != null && array.length > 0) {
+            for (int i : array) {
+                avg = sum((int) avg, i);
+            }
+            return avg / array.length;
+        }
+        return avg;
+    }
+
+    public boolean isSortedDescendant(int[] array) {
+        if (array != null) {
+            for (int i = 0; i < array.length - 1; i++) {
+                if (isGreater(array[i+1], array[i])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    public void cube(int[] array) {
+        if (array != null) {
+            for (int i = 0; i < array.length; i++) {
+                array[i] = mul(mul(array[i], array[i]), array[i]);
+            }
+        }
+    }
+
+    public boolean find(int[] array, int value) {
+        if (array != null) {
+            for (int i : array) {
+                if (isEqual(i, value)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    public void reverse(int[] array) {
+        if (array != null && array.length > 1) {
+            for (int i = 0, j = array.length - 1; i <= j; i++, j--) {
+                int temp = array[i];
+                array[i] = array[j];
+                array[j] = temp;
+            }
+        }
+    }
+
+    public boolean isPalindrome(int[] array) {
+        if (array != null) {
+            for (int i = 0, j = array.length - 1; i <= j; i++, j--) {
+                if (!isEqual(array[i], array[j])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    public int sum(int[][] matrix) {
+        int sum = 0;
+        if (matrix != null) {
+            for (int[] i : matrix) {
+                sum += sum(i);
+            }
+        }
+        return sum;
+    }
+
+    public int max(int[][] matrix) {
+        int max = Integer.MIN_VALUE;
+        if (matrix != null) {
+            for (int[] i : matrix) {
+                int tempMax = max(i);
+                if(isGreater(tempMax, max)){
+                    max = tempMax;
+                }
+            }
+        }
+        return max;
+    }
+
+    public int diagonalMax(int[][] matrix) {
+        int max = Integer.MIN_VALUE;
+        if(matrix != null) {
+            for (int i = 0; i < matrix.length; i++) {
+                if (isGreater(matrix[i][i], max)) {
+                    max = matrix[i][i];
+                }
+            }
+        }
+        return max;
+    }
+
+    public boolean isSortedDescendant(int[][] matrix) {
+        if(matrix != null){
+            for(int[] i: matrix){
+                if(!isSortedDescendant(i)){
+                    return false;
+                }
+            }
+        }
+        return true;
     }
 
 }