get, remove

Week 3: Objects, files and exceptions/4. Remove negative numbers - get, remove

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+Write the method
+
+void removeNegatives(ArrayList<Integer> numnbers) 
+
+...which removes all numbers less than zero from the list.
+
+Tip: the for loop may not work reliably if the iterated structure changes during loop execution 
+- you should use another way to iterate through the list instead.
+
+
+
+Example method call:
+public static void main(String[] parameters){
+    ArrayList<Integer> numbers = new ArrayList<>();
+    numbers.add(1);
+    numbers.add(-2);
+    numbers.add(-5);
+    numbers.add(10);
+    System.out.println(numbers);
+    removeNegatives(numbers);
+    System.out.println(numbers);
+}
+
+
+Program outputs:
+[1, -2, -5, 10]
+[1, 10]
+
+
+
+============================
+
+
+import java.util.Random;
+import java.util.ArrayList;
+
+public class Test{
+    public static void main(String[] args){
+        final Random r = new Random();
+        
+        
+        int[][] s = {{1,-2,3}, {10,-20,30,-40}, {-2,4,-6,8,-10}, {-9,-1,-8,2,7,3,-6,-4}};
+        
+        for (int[] pa : s) {
+            ArrayList<Integer> lista = new ArrayList<>();
+            for (int l : pa) lista.add(l);
+            
+            System.out.println("List before: ");
+            System.out.println("" + lista);
+            System.out.println("List after: ");
+            removeNegatives(lista);
+            System.out.println(lista);
+            System.out.println("");
+            
+        }
+    }
+    
+
+
+
+    // ADD
+    public static void removeNegatives(ArrayList<Integer> numbers) {
+        for (int i = 0; i < numbers.size(); i++) {
+            if (numbers.get(i) < 0) {
+                numbers.remove(i);
+                // because we remove the current idx
+                // adjust i by 1 (like as if we finished the previous 'i')
+                // System.out.println(i);
+                i--;
+                // System.out.println(i);
+            }
+        }
+    }
+
+
+
+
+}
+
+
+
+
+
+
+
+
+// Test1
+// List before: 
+// [1, -2, 3]
+// List after: 
+// 1
+// 0
+// [1, 3]
+
+// List before: 
+// [10, -20, 30, -40]
+// List after: 
+// 1
+// 0
+// 2
+// 1
+// [10, 30]
+
+// List before: 
+// [-2, 4, -6, 8, -10]
+// List after: 
+// 0
+// -1
+// 1
+// 0
+// 2
+// 1
+// [4, 8]
+
+// List before: 
+// [-9, -1, -8, 2, 7, 3, -6, -4]
+// List after: 
+// 0
+// -1
+// 0
+// -1
+// 0
+// -1
+// 3
+// 2
+// 3
+// 2
+// [2, 7, 3]
+
+
+
+
+
+
+
+
+List before: 
+[1, -2, 3]
+List after: 
+[1, 3]
+
+List before: 
+[10, -20, 30, -40]
+List after: 
+[10, 30]
+
+List before: 
+[-2, 4, -6, 8, -10]
+List after: 
+[4, 8]
+
+List before: 
+[-9, -1, -8, 2, 7, 3, -6, -4]
+List after: 
+[2, 7, 3]
+
+
+
+