X32专项练习部分12

• 4种引用类型
• 线程锁释放
• for循环执行顺序
• Integer类的常用方法
• 三角函数
• GC垃圾回收机制
• 值传递开辟内存空间
• Java创建对象的5种方式
• 总目录

class Test4 {
    static boolean foo(char c) {
        System.out.print(c); // ABDCBDCB
        return true;
    }

    public static void main(String[] args) {
        int i = 0;
        for (foo('A'); foo('B') && (i < 2); foo('C')) {
            i++;
            foo('D');
        }
    }
    
}

public static void main(String[] args) {
        int a = Integer.parseInt("1024");

        int b = Integer.valueOf("1024").intValue();

        

        System.out.println(judgeTypeInteger(a)); // true
        System.out.println(judgeTypeInteger(b)); // true
        System.out.println(a == b); // true

        
}

		double d = Math.cos(42);
        // double d1 = Math.cosine(42); // cosine方法不存在
        double d2 = Math.cos(Math.toRadians(42));
        double d3 = Math.cos(Math.toDegrees(42));
        System.out.println(d + " " + d2 + " " + d3);
        // -0.39998531498835127 0.7431448254773942 0.9993069281930212
        // 科学计算器算出的结果是 0.74314482547739423501469704897426

        

class Test7 {
    public static void main(String[] args) {
        int x1 = 127;
        int x2 = 129;

        int identityHashCode = System.identityHashCode(x1);
        System.out.println("传递之前：x1 identityHashCode = "+identityHashCode);

        identityHashCode = System.identityHashCode(x2);
        System.out.println("传递之前：x2 identityHashCode = "+identityHashCode);

        System.out.println("-----------------------------------------");
        method(x1);
        method(x2);
    }

    public static void method(int x) {
        int identityHashCode = System.identityHashCode(x);
        System.out.println("传递之后：x identityHashCode = "+identityHashCode);
    }
    
}