public class testEquals { public static void main(String[] args) { Integer i = 1; System.out.println("1".equals(i)); } }
这里理所当然以为"1".equals(i.toString()) i 会自动调用toString()方法,通过查看源码
public boolean equals(Object anObject) { if (this == anObject) { return true; } if (anObject instanceof String) { String anotherString = (String) anObject; int n = value.length; if (n == anotherString.value.length) { char v1[] = value; char v2[] = anotherString.value; int i = 0; while (n-- != 0) { if (v1[i] != v2[i]) return false; i++; } return true; } } return false; }
这里首先会判断两个对象地址是否相同,地址相同则对象一定相同,然后判断是否是同一类型,Integer显然不是String类型,所以这里不会相等!!!
public class testEquals { public static void main(String[] args) { Integer i = 1; System.out.println("1".equals(i.toString()));//true } }显示调用toString()将 i 转换成了字符串结果才为true