upd lab3 // add todo for lab4

This reverts commit 29e63163a4.

src/Lab2.java

@@ -1,13 +1,44 @@
 public class Lab2 {
     public static void main(String[] args) {
-        int[] array = {1, 2, 3};
+        final int A = 2;
-        /*for (int i = 0; i < array.length; i++) {
+        final int[][] MATRIX_B = {
+                {1, 202, 1, 1, 202, 3, 1, 202, 3,},
+                {1, 202, 1, 1, 202, 3, 1, 202, 3, 4},
+                {1, 1,   3, 1, 202, 3, 1, 202, 3,},
+//                {4, 5, 6,},
+        };
+
+        int[][] MATRIX_C = multiplication(A, MATRIX_B);
+
+        print(MATRIX_C);
+
+//        System.out.println("Sum of smallest elements in every column: " + sumOfSmallestElementsInEveryColumn(MATRIX_C));
+        try {
+            System.out.println("Sum of smallest elements in every column: " + sumOfSmallestElementsInEveryColumnRenew(MATRIX_C));
+            System.out.println("???...");
+        } catch (Exception e) {
+            System.err.println(e.getMessage());
+        }
+
+        System.out.println("I'm still working...");
+
+        /*int[] array = {1, 2, 3};
+        int[] array2 = new int[3];
+        Object[] array3 = new String[3];
+        System.out.println(array3[0]); //nothing, trash from the memory, null || null
+        System.out.println(array2[0]); //nothing, trash from the memory, null || 0
+        System.out.println(array[0]); // || 1
+
+        int[][] matrix2 = new int[2][3];
+        matrix2[0] = new int[2];
+        matrix2[1] = new int[1];
+        for (int i = 0; i < array.length; i++) {
             if (i % 2 == 0) {
                 System.out.println("!" + array[i]);
             } else {
                 System.out.println("?" + array[i]);
             }
-        }*/
+        }
 
         for (int i = 0; i < array.length; i+=2) {
             System.out.println("!" + array[i]);
@@ -22,5 +53,88 @@ public class Lab2 {
                 {1, 2},
                 {3}
         };
+
+//        C=a×B, a - const
+
+
+//        final int[][] MATRIX_C = int;
+
+
+        MATRIX_B[0][0] = 2;
+        MATRIX_B[0] = new int[]{1, 2};
+        System.out.println(MATRIX_B[0][0]);
+        MATRIX_B = new int[][]{
+                {1, 2},
+                {3}
+        };*/
+    }
+
+    private static int sumOfSmallestElementsInEveryColumn(final int[][] MATRIX_C) {
+//        todo check different length of rows
+//        todo try to change i and j
+//        todo check repetition of minimal elements
+        int sum = 0;
+        for (int i = 0; i < MATRIX_C[0].length; i++) {
+            int tmpSmallest = MATRIX_C[0][i];
+            for (int j = 1; j < MATRIX_C.length; j++) {
+                if (MATRIX_C[j][i] < tmpSmallest) {
+                    tmpSmallest = MATRIX_C[j][i];
+                }
+            }
+            sum += tmpSmallest;
+        }
+        return sum;
+    }
+
+    private static int sumOfSmallestElementsInEveryColumnRenew(final int[][] MATRIX_C) throws Exception {
+//        todo check different length of rows
+        for (int i = 1; i < MATRIX_C.length; i++) {
+            if (MATRIX_C[i].length != MATRIX_C[0].length) {
+                throw new /*Runtime*/Exception("There are different lengths of matrix rows.");
+//                System.err.println("There are different lengths of matrix rows.");
+//                System.exit(0);
+            }
+        }
+        int sum = 0;
+        for (int j = 0; j < MATRIX_C[0].length; j++) {
+            int tmpSmallest = MATRIX_C[0][j];
+            boolean valueRepeats = false;
+            for (int i = 1; i < MATRIX_C.length; i++) {
+                if (MATRIX_C[i][j] < tmpSmallest) {
+                    tmpSmallest = MATRIX_C[i][j];
+                    valueRepeats = false;
+                } else if (MATRIX_C[i][j] == tmpSmallest) {
+                    valueRepeats = true;
+                }
+            }
+            sum += tmpSmallest;
+
+            if (!valueRepeats) {
+                sum += tmpSmallest;
+            }
+        }
+        return sum;
+    }
+
+    private static void print(final int[][] MATRIX_C) {
+        for (int i = 0; i < MATRIX_C.length; i++) {
+            for (int j = 0; j < MATRIX_C[i].length; j++) {
+//                System.out.print(MATRIX_C[i][j] + "\t");//printf("%4d",
+                System.out.printf("%4d ", MATRIX_C[i][j]);//printf("%4d",
+            }
+            System.out.println();
+        }
+    }
+
+    private static int[][] multiplication(int A, final int[][] MATRIX_B) {
+        final int[][] MATRIX_C = new int[MATRIX_B.length][/*MATRIX_B[0].length*/]; // todo !!!DANGER different lengths of rows
+//        final int[][] MATRIX_C = MATRIX_B;
+        for (int i = 0; i < MATRIX_B.length; i++) {
+            MATRIX_C[i] = new int[MATRIX_B[i].length];
+            for (int j = 0; j < MATRIX_B[i].length; j++) {
+                MATRIX_C[i][j] = MATRIX_B[i][j] * A;
+            }
+        }
+        return MATRIX_C;
     }
 }

src/Lab3.java

@@ -0,0 +1,36 @@
+public class Lab3 {
+    public static void main(String[] args) {
+        String s = "ASD";
+
+        StringBuilder stringBuilder = new StringBuilder("ASD");
+
+        stringBuilder.append("A");
+
+        String s2 = s;
+        System.out.println("s2 = " + s2);
+        System.out.println(s == s2); // true?
+        System.out.println(s.equals(s2)); // true?
+        s += "B";
+        System.out.println(s);
+        System.out.println("s2 = " + s2);
+
+        System.out.println(s == s2); // false?
+        System.out.println(s.equals(s2)); // false?
+
+        String s3 = new String("ASD");
+        System.out.println(s3 == s2); // true? (false)
+        System.out.println(s3.equals(s2)); // false? (true)
+
+//      String Pool
+        String s4 = "ASD";
+//        String s5 = new String("ASD");
+        String s5 = "AS";
+        s5 += "D";
+        System.out.println(s4 == s5); // true? (SP)
+        System.out.println(s4.equals(s5)); // (true)
+
+
+
+        System.out.println("Done!");
+    }
+}

src/lab4/Main.java

@@ -0,0 +1,7 @@
+package lab4;
+
+public class Main {
+    public static void main(String[] args) {
+        //todo equals+hashcode
+    }
+}

src/test/Test.java

@@ -0,0 +1,13 @@
+package test;
+
+public class Test {
+    public static void main(String[] args) {
+
+    }
+    static int m(){
+        System.exit(0);
+//        return 1;
+        System.out.println(123);
+        return 1;
+    }
+}