JDK 5.0 new features automatic boxing and automatic unboxing

/*
	 * JDK 5.0 新特性 自动装箱与自动拆箱
	 * */
	@Test
	public void test3(){
		//int num1 = 11;
		//基本数据类——》包装类对象
		//method(num1);
		
		//自动装箱
		int num2 = 10;
		Integer in1 = num2;
		
		//自动拆箱
		//包装类——》基本数据类型
		System.out.println(in1.toString());
		
		int num3 = in1;  //自动拆箱
		System.out.println(num3);
	}
	
	public void method(Object obj){
		System.out.println(obj);
	}

exercise

@Test
	public void test3(){
		Integer i = new Integer(1);
		Integer j = new Integer(1);
		System.out.println(i == j);  //false
		
		Integer m = 1;
		Integer n = 1;
		System.out.println(m == n);  //true
		
		Integer x = 128;
		Integer y = 128;
		System.out.println(x == y);   //false
	}

Integer internally defines the IntegerCache structure, IntegerCache defines Integer[],

Integers ranging from -128 to 127 are saved. If we use auto-boxing, the value of Integer is in the range of -128 to 127, and you can directly

Use the elements in the array instead of going to new.