Java 装箱 拆箱

public class WrapperTest {
	// 基本数据类型--->包装类：调用包装类的构造器
	@Test
	public void test1() {
		int num1 = 10;
		Integer in1 = new Integer(num1);
		System.out.println(in1.toString());//10
		Integer in2 = new Integer("123");
		System.out.println(in2.toString());//123
		// 报异常:NumberFormatException
		Integer in3 = new Integer("123abc");//调用Integer必须全是数字
		System.out.println(in3.toString());
		//有点特殊：因为底层源码 return ((s != null) && s.equalsIgnoreCase("true"));
		Boolean b1 = new Boolean(true);
		Boolean b2 = new Boolean("True");//true
		System.out.println(b2);
		Boolean b3 = new Boolean("true123");//flase
		Order order = new Order();
		System.out.println(order.isMale);//false//因为基本数据类型的默认初始化值为：false
		System.out.println(order.isFamale);//null//此时为引用数据类型(类),默认初始化值：null
	}
}
class Order {
	boolean isMale;
	Boolean isFamale;
}

public class WrapperTest {
	@Test
	public void test2() {
		Integer in1 = new Integer(12);
		int i1 = in1.intValue();
		System.out.println(i1 + 1);//13
		Float f1 = new Float(12.3);
		float f2 = f1.floatValue();
		System.out.println(f2 + 1);//13.3
	}
}

public class WrapperTest {
	@Test
	public void test3() {
		//自动装箱
		int num2 = 10;
		Integer in1 = num2;
		boolean b1 = true;
		Boolean b2 = b1;
		//自动拆箱
		System.out.println(in1.toString());
		int num3 = in1;
	}
}

public class WrapperTest {
	@Test
	public void test4() {
		//方式一：连接运算
		int num1 = 10;
		String str1 = num1 + "";
		//方式二：调用String的valueOf(Xxx xxx)
		float f1 = 12.3f;
		String str2 = String.valueOf(f1);
		Double d1 = new Double(12.4);
		String str3 = String.valueOf(d1);
		System.out.println(str2);//"12.3"
		System.out.println(str3);//"12.4"	
	}
}

public class WrapperTest {
	@Test
	public void test5() {
		String str1 = "123";
		int num2 = Integer.parseInt(str1);//若为"123a",则会报NumberFormatException
		System.out.println(num2 + 1);
		String str2 = "true";
		boolean b1 = Boolean.parseBoolean(str2);//非true,即flase
		System.out.println(b1);
	}