جافا Java

❓ continue مع الأعداد الزوجية continue with evens

int s = 0;
for (int i = 1; i <= 4; i++) {
  if (i % 2 == 1) continue;
  s += i;
}
System.out.println(s);

❓ حساب على char char arithmetic

char c = 'A';
c += 2;
System.out.println(c);

❓ ثبات toString مقابل تعديل StringBuilder StringBuilder mutability

StringBuilder sb = new StringBuilder("a");
String s = sb.toString();
sb.append("b");
System.out.println(s);

❓ إزالة أثناء for-each Removing during for-each

import java.util.*;
List<Integer> list = new ArrayList<>(java.util.Arrays.asList(1,2,3));
for (Integer v : list) {
  if (v == 2) list.remove(v);
}
System.out.println(list.size());

❓ نسخ المصفوفة copyOf Arrays.copyOf clone

int[] x = {1,2};
int[] y = java.util.Arrays.copyOf(x, x.length);
y[0] = 9;
System.out.println(x[0]);

❓ حقول مقابل دالة مُعاد تعريفها Fields vs overridden method

class A { int v = 1; int get(){ return v; } }
class B extends A { int v = 2; int get(){ return v; } }
A a = new B();
System.out.println(a.v + "," + a.get());

❓ اختيار overload مع null Overload resolution with null

void f(Object o){ System.out.print("O"); }
void f(String s){ System.out.print("S"); }
f(null);

❓ تمرير مصفوفة لميثود Passing array to method

static void inc(int[] a){
  for (int i = 0; i < a.length; i++) a[i]++;
}
int[] a = {0,1,2};
inc(a);
System.out.println(a[2]);

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❓ switch مع break switch with break

int n = 1;
switch (n) {
  case 1: System.out.print("X"); break;
  default: System.out.print("Y");
}