Java 如何判断Integer类型的值是否相等

public class Demo { 
    public static void main(String[] args) {
        Integer c = -128;
        Integer d = -128;
        System.out.println("c == d: " + (c == d));
        System.out.println("c.equals(d): " + c.equals(d));
        System.out.println("c.intValue() == d.intValue(): " + (c.intValue() == d.intValue()));
        System.out.println("Objects.equals(c, d): " + Objects.equals(c, d));
        
        Integer e = 127;
        Integer f = 127;
        System.out.println("e == f: " + (e == f));
        System.out.println("e.equals(f): " + e.equals(f));
        System.out.println("e.intValue() == f.intValue(): " + (e.intValue() == f.intValue()));
        System.out.println("Objects.equals(e, f): " + Objects.equals(e, f));
        
        Integer g = 128;
        Integer h = 128;
        System.out.println("g == h: " + (g == h));
        System.out.println("g.equals(h): " + g.equals(h));
        System.out.println("g.intValue() == h.intValue():" + (g.intValue() == h.intValue()));
        System.out.println("Objects.equals(g, h): " + Objects.equals(g, h));
    }
}

/**
     * Cache to support the object identity semantics of autoboxing for values between
     * -128 and 127 (inclusive) as required by JLS.
     *
     * The cache is initialized on first usage.  The size of the cache
     * may be controlled by the -XX:AutoBoxCacheMax=<size> option.
     * During VM initialization, java.lang.Integer.IntegerCache.high property
     * may be set and saved in the private system properties in the
     * sun.misc.VM class.
     */
 
    private static class IntegerCache {
        static final int low = -128;
        static final int high;
        static final Integer cache[]; 
        static {
            // high value may be configured by property
            int h = 127;
            String integerCacheHighPropValue =
                sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
            if (integerCacheHighPropValue != null) {
                int i = parseInt(integerCacheHighPropValue);
                i = Math.max(i, 127);
                // Maximum array size is Integer.MAX_VALUE
                h = Math.min(i, Integer.MAX_VALUE - (-low));
            }
            high = h;
 
            cache = new Integer[(high - low) + 1];
            int j = low;
            for(int k = 0; k < cache.length; k++)
                cache[k] = new Integer(j++);
        } 
        private IntegerCache() {}
    }

 Integer newInt = new Integer(10);
 //自动装箱操作，编译后class文件中为：Integer num = Integer.valueOf(10);
 Integer num = 10;
 //num.intValue()为解包操作
 int intNum = num.intValue();
 /**
  * 输出结果为true----false----true，原因：
  * 1、 Integer为引用类型,引用类型栈中变量表示一个地址指向堆中的一片内存空间
  * 2、 newInt.equals(num)为true是因为Integer重写了equals方法，equals方法中实际是值比较
  * 3、(newInt == num)为false因为两个变量不指向同一片内存
  * 4、(intNum==num)结果为true是因为intNum是基本数据类型，值直接存在栈中，两者比较的是值
  */
 System.out.println(newInt.equals(num)+"----"+(newInt == num)+"----"+(intNum==num));

    private final int value;
    public boolean equals(Object obj) {
        if (obj instanceof Integer) {
         //将对象强制转换为Integer类型，然后自动拆箱进行==比较
            return value == ((Integer)obj).intValue();
        }
        return false;
    }

 public Integer(int value) {
  //参数为int 直接赋值
  this.value = value;
 }
 public Integer(String s) throws NumberFormatException {
  //参数为String的情况下调用paseInt()方法进行赋值，10表示为按10进制转换
  this.value = parseInt(s, 10);
 }