截取出的字符串进行判断？？

Question

String a="11111111111111";
String b=a.substring(0,3);
System.out.println(b=="111");

为什么答案是false求jie'da

Answer 1

看substring方法实现 就知道了 返回的是一个新的字符串对象
public String substring(int beginIndex, int endIndex) {

if (beginIndex < 0) {

throw new StringIndexOutOfBoundsException(beginIndex);

}

if (endIndex > value.length) {

throw new StringIndexOutOfBoundsException(endIndex);

}

int subLen = endIndex - beginIndex;

if (subLen < 0) {

throw new StringIndexOutOfBoundsException(subLen);

}

return ((beginIndex == 0) && (endIndex == value.length)) ? this

: new String(value, beginIndex, subLen);

}