String类的compareTo方法的源码解析

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String类的compareTo方法的源码如下：

class String {
......
private final char value[]; // 数组常量表示数组大小(长度)不能变。

// 在底层会有一个转换，直接将字符串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; // 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;
}
......
}

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示例代码：

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