String类的compareTo()方法的源码解析

private final char value[];

字符串会自动转换为一个字符数组。

public int compareTo(String anotherString) {
//this -- s1 -- "hello"
//anotherString -- s2 -- "hel"

int len1 = value.length; //this.value.length--s1.toCharArray().length--5
int len2 = anotherString.value.length;//s2.value.length -- s2.toCharArray().length--3
int lim = Math.min(len1, len2); //Math.min(5,3); -- lim=3;
char v1[] = value; //s1.toCharArray()
char v2[] = anotherString.value;

//char v1[] = {'h','e','l','l','o'};
//char v2[] = {'h','e','l'};

int k = 0;
while (k < lim) {
char c1 = v1[k]; //c1='h','e','l'
char c2 = v2[k]; //c2='h','e','l'
if (c1 != c2) {
return c1 - c2;
}
k++;
}
return len1 - len2; //5-3=2;
}

String s1 = "hello";
String s2 = "hel";
System.out.println(s1.compareTo(s2)); // 2