String

public final class String implements java.io.Serializable, Comparable, CharSequence

1.构造函数

其实一般String都不用构造函数,直接用=号就可以了.

a.常用的构造函数:

public String(char value[])
public String(char value[], int offset, int count)

b.几乎不用的构造函数

public String()//几乎不使用
public String(String original)
几乎不用,应该使用String s="HelloWorld";而不是String s=new String("HelloWorld");
public String(byte bytes[], int offset, int length, String charsetName)
public String(byte bytes[], String charsetName)
public String(byte bytes[], int offset, int length)
public String(byte bytes[])
我都不知道还有这些

c.过时的

public String(byte ascii[], int hibyte, int offset, int count)
public String(byte ascii[], int hibyte)

2.常用方法

public int length()//该方法返回字符串长度,也就是字符的个数,不是字节大小,求字节大小应该为2*length()
public char charAt(int index)//指定位置的字符
public boolean equals(Object anObject)//比较两个字符串
public boolean equalsIgnoreCase(String anotherString)//比较两个字符串,忽略大小写
public byte[] getBytes()
public byte[] getBytes(String charsetName)
public boolean startsWith(String prefix, int toffset)
public boolean startsWith(String prefix)
public boolean endsWith(String suffix)
public int hashCode()
public int indexOf(int ch)
public int indexOf(int ch, int fromIndex)
public int lastIndexOf(int ch)
public int lastIndexOf(int ch, int fromIndex)
public int indexOf(String str)
public int indexOf(String str, int fromIndex)
public int lastIndexOf(String str)
public int lastIndexOf(String str, int fromIndex)
public String substring(int beginIndex)
public String substring(int beginIndex, int endIndex)
public CharSequence subSequence(int beginIndex, int endIndex)
public String replace(char oldChar, char newChar)
public String toLowerCase(Locale locale)
public String toLowerCase()
public String toUpperCase(Locale locale)
public String toUpperCase()
public String trim()
public char[] toCharArray()
public static String valueOf(Object obj)
public static String valueOf(char data[])
public static String valueOf(char data[], int offset, int count)
public static String valueOf(boolean b)
public static String valueOf(char c)
public static String valueOf(int i)
public static String valueOf(long l)
public static String valueOf(float f)
public static String valueOf(double d)

3.很少用的方法

public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin)
public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin)
public boolean contentEquals(StringBuffer sb)
public int compareTo(String anotherString)
public int compareTo(Object o)//实现Comparable接口的方法
public int compareToIgnoreCase(String str)
public String concat(String str)//因为可以用+号,所以很少用这个了
public String toString()
public native String intern()

4.多余的方法

public static String copyValueOf(char data[], int offset, int count)
public static String copyValueOf(char data[])

5.难用的方法

public boolean matches(String regex)
public String replaceFirst(String regex, String replacement)
public String replaceAll(String regex, String replacement)
public String[] split(String regex, int limit)
public String[] split(String regex)
//以上方法都和正则表达式有关,是比较难用的.

6.想不通的

public static final Comparator CASE_INSENSITIVE_ORDER
//这个是用来实现比较String大小写不敏感的比较器,为什么要设为public呢,它只对String有用,根本就不应该为public.

public boolean regionMatches(int toffset, String other, int ooffset,int len)
public boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)
//我认为这两个也不应该public