04-String课后动手动脑
一.String.equals()方法
public final class String
implements java.io.Serializable, Comparable<String>, CharSequence {
/** The value is used for character storage. */
private final char value[];
/** Cache the hash code for the string */
private int hash; // Default to 0
/**
* Initializes a newly created {@code String} object so that it represents
* an empty character sequence. Note that use of this constructor is
* unnecessary since Strings are immutable.
*/
public String() {
this.value = new char[0];
}
/**
* Initializes a newly created {@code String} object so that it represents
* the same sequence of characters as the argument; in other words, the
* newly created string is a copy of the argument string. Unless an
* explicit copy of {@code original} is needed, use of this constructor is
* unnecessary since Strings are immutable.
*
* @param original
* A {@code String}
*/
public String(String original) {
this.value = original.value;
this.hash = original.hash;
}
/**
* Compares this string to the specified object. The result is {@code
* true} if and only if the argument is not {@code null} and is a {@code
* String} object that represents the same sequence of characters as this
* object.
*
* @param anObject
* The object to compare this {@code String} against
*
* @return {@code true} if the given object represents a {@code String}
* equivalent to this string, {@code false} otherwise
*
* @see #compareTo(String)
* @see #equalsIgnoreCase(String)
*/
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;
}
二.String 方法使用说明：
1.Length()：返回当前字符串长度
用法：int 变量名=字符串名.length();
2.charAt(int index): 取字符串中的某一个字符，其中的参数index指的是字符串中序数。字符串的序数从0开始到length()-1。
例：String s=new String(“abcde”); 能得到s.charAt(4)==’e’;
3.getChars():从这个字符串中的字符复制到目标字符数组
用法：字符串名.getChars()
4.replace(char oldChar,char newChar):将字符串中第一个oldChar替换成newChar.
5.toUpperCase():用于把字符串转换为大写。
用法：字符串名.toUpperCase()
6.toLowerCase():方法返回一个字符串，该字符串中的字母被转换为小写字母。
用法：字符串名.toLowerCase()
7.trim():调用字符串对象的一个副本，但是所有起始和结尾的空格都被删除了
例：String s=" Hello World ".trim();就是把"Hello World"放入s中。
8.toCharArrary():将该String对象转化为char数组
例：char []c=字符串名字.toCharArray();
