String . String , , 0 2*109. String , :
A, abcd, abcd, , .
. - .
. , \n. , .
, .
Java . A , 'A' ASCII A. .
: s1 s2 , s1+s2 , () , s1 s2. ,
String s= + ;
s .
+=. s1 s2
s1+=s2 s1=s1+s2.
( ) String. String , , . , . , .
==. ,
String s1=" String";
String s2="";
s2+=" String";
if(s1==s2)
System.out.println("s1 s2");
else
System.out.println("s1 s2");
s1 s2, - . equals. s1==s2 s1.equals(s2), s1 s2.
,
String s1="";
String s2="";
if(s1==s2)
System.out.println("s1 s2");
else
System.out.println("s1 s2");
s1 s2. , Java , -.
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, , , , .
String . . s1 subS String, charArray char[], ch1 char, i, index1 count (, ) .
String.valueOf() String, . .
String.valueOf(charArray, index1,count) , , count , index1.
String . .
s1.charAt(i) s1, i ( ).
s1.endsWith(subS) true , s1 , subS.
s1.equals(subS) - true , , s1, , subS.
s1.equalsIgnoreCase(subS) , ( ).
s1.getBytes() byte[], - .
s1.getBytes(charset) , (charset). charset ISO-8859-1 ( 8- ), UTF-8, UTF-16 ( UNICODE) .
s1.indexOf(subS) , s1 subS.
s1.indexOf(subS,i) i, s1 subS.
s1. lastIndexOf (subS) , s1 subS.
s1. lastIndexOf (subS,i) i, s1 subS.
s1.length() ( 16- UNICODE, ). .
s1.replaceFirst(oldSubS,newSubS) s1, oldSubS newSubS.
s1.replaceAll(oldSubS,newSubS) s1, oldSubS newSubS.
s1.split(separator) String[], s1 , separator. , separator, . .
s1.split(separator, i) , i . s1, , . i 0 , . i <0 , .
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s1.startsWith(subS) true , s1 subs.
s1.startsWith(subs, index1) true , s1 index1 subs.
s1.substring(index1) , s1 index1.
s1.substring(index1,index2) , s1 index1 index2.
s1.toCharArray() , s1.
s1.toLowerCase() , s1, ( ). , (locale).
s1.toUpperCase() - , s1, ( ). , (locale).
s1.trim() s1, .
Object toString(), . , , . Object ( ), @, - (, ) . -, , . . , toString() . - , ( Char) - .
+ += , , , toString() . () . , . ,
String s=1+2+3;
s==6.
String s= =+1+2+3;
=123. , , . =+1. , . toString(), . =1. =1 2. toString(), . =12. =12 3.
String s=1+2+ +1+2;
,
3 12.
, . , ?: , .
, . ,
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Byte.parseByte()
Short.parseShort()
Integer.parseInt()
Long.parseLong()
Float.parseFloat()
Double.parseDouble()
valueOf(), Byte, Short, Character, Integer, Long, Float, Double. ,
Byte.valueOf(), ..
, Integer Long :
Integer.toBinaryString()
Integer.toHexString()
Long.toBinaryString()
Long.toHexString()
(Byte, Short, Integer, Long) decode:
Byte.decode(), ..
:
Character.isDigit() , , .
Character.isLetter() , , .
Character.isLetterOrDigit() , , .
Character.isLowerCase() , , .
Character.isUpperCase() , , .
Character.isWhitespace() , , , , ..
, StringBuffer StringBuilder. , ( , , ). , , String. StringBuffer , (threads) , String StringBuilder, . StringBuilder, JDK 1.5, , . ( ).
, , . StringBuffer StringBuilder sb.append(s), sb s. sb.insert(index,s), , index, s.
:
StringBuffer sb=new StringBuffer();
sb.append(" StringBuffer");
sb.insert(0," ");
System.out.println(sb);
append insert
:
s1.contentEquals(sb) , true , s1 , sb.
java.awt.Graphics. , .
, w- , h- ; x,y- . x,y- , .
Color getColor() | . |
setColor(Color c) | . |
Font getFont() | . |
setFont(Font f) | . Font( , , ) |
FontMetrics getFontMetrics() | |
FontMetrics getFontMetrics(Font f) | f |
setXORMode(Color c1) | XOR ( ) c1. color , color ^ c1 ( color XOR c1) RGB- . . |
setPaintMode() | XOR. |
translate(x0,y0) | x0,y0. , , . |
drawLine(x1,y1,x2,y2) | x1,y1 x2,y2 |
drawRect(x,y,w,h) | . |
drawRoundRect(x,y,w,h,arcWidth,arcHeight) | . |
draw3DRect(x,y,w,h,isRaised) | . isRaised ==true, (raised), - . |
drawPolygon(Polygon p); drawPolygon(int[] xPoints, int[] yPoints, int nPoints) | , nPoints . |
drawPolyline(int[] xPoints,int[] yPoints, int nPoints) | , nPoints . |
drawOval(x,y,w,h) | . |
drawArc(x,y,w,h,startAngle,arcAngle) | . startAngle , arcAngle, . |
drawImage(Image img,int x,int y, ImageObserver observer) | . |
clearRect(x,y,w,h) | ( ) |
fillRect(x,y,w,h) | , . |
fillRoundRect(x,y,w,h,arcWidth,arcHeight) | , . |
fill3DRect(x,y,w,h, isRaised) | , . isRaised ==true, (raised), - . |
fillPolygon(Polygon p) fillPolygon(int[] xPoints, int[] yPoints, int nPoints) | , . |
fillOval(x,y,w,h) | , . |
fillArc(x,y,w,h,startAngle,arcAngle) | , . , , . |
copyArea(x,y,w,h,dx,dy) | , dx,dy |
drawString(s,x,y) | s |
drawChars(char[] data,int offset,int length,int x,int y) | |
drawBytes(byte[] data,int offset,int length,int x,int y) | , |
setClip(x,y,w,h) setClip(Shape clip) | . ( ). |
clipRect(x,y,w,h) | . |
Rectangle getClipBounds() Rectangle getClipBounds(Rectangle r) | , . |
Graphics create() | g1=g.create()- g |
dispose() | - ( , ). |
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, .
java.awt.Graphics g,g1;
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
java.awt.Graphics g,g1;
g=jPanel1.getGraphics();
int x1=20,x2=120,y1=20,y2=120;
int x3=20,y3=20,w3=60,h3=80;
int x4=30,y4=60,w4=30,h4=40;
int x0=10,y0=10,w0=10,h0=10;
int w1=80,h1=120;
g.setClip(0,0,60,80);//
g.drawLine(x1,y1,x2,y2);//
g.drawOval(x3,y3,w3,h3);//
g.clipRect(x4,y4,20,20);//
g.clearRect(x4,y4,w4,h4);//
g.setClip(0,0,200,280); //
g.copyArea(x1,y1,w1,h1,60,0);
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g.draw3DRect(10,20,w1,h1,false);
g.drawPolygon(new java.awt.Polygon(new int[]{10,10,20,40},
new int[]{10,20,30,60},4));
}
: . , .
, , paint, . :
public void paint(java.awt.Graphics g){
super.paint(g);
g=jPanel1.getGraphics();
...
}
, ,
private void jPanel1ComponentResized (java.awt.event.ComponentEvent evt) {
...
}
, , . . .
- . , . update(Graphics g). :
for(int i=0;i<=100;i++){
FiguresUtil.moveFigureBy(figure,dx,dy);
update(g);
};
. , . : , . , , .