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();