Java での自動ボックス化とボックス化解除についての深い理解

Integer i1=3;
int i2=i1;

Integer a = 100;
int b = 100;
System.out.println(a==b);结果为 true

Integer a = 100;
Integer b = 100;
System.out.println(a==b);//结果为true
Integer a = 200;
Integer b = 200;
System.out.println(a==b);//结果为false

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) {
            try {
                int i = parseInt(integerCacheHighPropValue);
                i = Math.max(i, 127);
                // Maximum array size is Integer.MAX_VALUE
                h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
            } catch( NumberFormatException nfe) {
                // If the property cannot be parsed into an int, ignore it.
            }
        }
        high = h;

        cache = new Integer[(high - low) + 1];
        int j = low;
        for(int k = 0; k < cache.length; k++)
            cache[k] = new Integer(j++);

        // range [-128, 127] must be interned (JLS7 5.1.7)
        assert IntegerCache.high >= 127;
    }

Integer a = new Integer(100);
Integer b = 100;
System.out.println(a==b);
//结果为false

Integer a = 100;
Integer b= 100;
System.out.println(a == b);
//结果true
a = 200;
b = 200;
System.out.println(c == d);
//结果为false