useageguides.java

一些常用的java程序,包括swing.net.io,matrix等

package useageOfString;

public class UseageGuides {
	
	//the instance of class String, if bulit, can't be changed any more.But StringButter's instance can
	// s1 = "123"+45+678 is different from s2 = 123+45+"678"  s2 is same with "168678"
	
	//-----------------------------------------------------------------
	
	//      parse object to string, if obj == null, return "null", or call obj.toString()
	//public static String str.valueOf(boolean b);   all from java.lang.String
	//public static String str.valueOf(char c);
	//public static String str.valueOf(int i);
	//public static String str.valueOf(long l);
	//public static String str.valueOf(float f);
	//public static String str.valueOf(double d);
	
	//-----------------------------------------------------------------
	
	//  String compare
	//public int str.compareTo(String anotherString)    return this.charAt(k) - anotherString.charAt(k)  k = 0,1,2
	//public int str.length()
	//public char str.charAt(int index)  return the (index+1)th char, thus "THU".charAt(0) == 'T'  "abc".compareTo("ABC") == 32
	//public boolean str.equals(Object anobj)  def if two string is the same, but not pointer to the same
	//public boolean str.equalsIgnoreCase(String astr)  ignore case
	//  ==  pointer to the same
	
	//-----------------------------------------------------------------
	
	// String to other obj, such as Integer, Boolean, Double
	//false: Boolean.parseBoolean(null) Boolean.parseBoolean("false") Boolean.parseBoolean(null)("ABC")
	//Integer.parseInt(String str)
	//Double.parseDouble(String str)
	
	//-----------------------------------------------------------------
	
	//StringBuffer
	//StringBuffer's method: public String strbuf.toString()
	//new StringBuffer(str)
	
	//-----------------------------------------------------------------
	//string array: String [] s = {new String("abc"), new String("efg"), new String("justok")};
	//				String [] s = new String[3]  ---- not new String(3)
	
}