Strategy

Strategy：定义一系列的算法,把它们一个个封装起来, 并且使它们可相互替换。本模式使得算法的变化可独立于使用它的客户。

Stratrgy应用比较广泛,比如, 公司经营业务变化图, 可能有两种实现方式,一个是线条曲线,一个是框图(bar),这是两种算法,可以使用Strategy实现.

step1:define a interface or abstract class ,for example Class stragety.

step2:define subclasses to implement the interface or extend the abstract class,for example Class strategyA or strategyB

step3:define a class for the user to choose the stragety ,for example ChooseStragety

code:

step1:

public interface Strategy {
public void drawText(String s, int lineWidth, int lineCount);
}

step2:

public class StrategyA implements Strategy {
public StrategyA() {
}
public void drawText(String text, int lineWidth, int lineCount) {
if(lineWidth > 0) {
int len = text.length();
int start = 0;
System.out.println("----- String length is :" + len + ", line width is :" + lineWidth);
while(len > 0) {
if(len <= lineWidth) {
System.out.println(text.substring(start));
} else {
System.out.println(text.substring(start, start+lineWidth));
}
len = len - lineWidth;
start += lineWidth;
}
} else {
System.out.println("line width can not < 1 !");
}
}
}

public class StrategyB implements Strategy {
public StrategyB() {
}
public void drawText(String text, int lineWidth, int lineCount) {
if(lineCount > 0) {
int len = text.length();
//System.out.println(Math.ceil(len/lineCount));
lineWidth = (int)Math.ceil(len/lineCount) + 1;
int start = 0;
System.out.println("----- There are " + lineCount + " Line, " + lineWidth + "char per line -----");
while(len > 0) {
if(len <= lineWidth) {
System.out.println(text.substring(start));
} else {
System.out.println(text.substring(start, start+lineWidth));
}
len = len - lineWidth;
start += lineWidth;
}
} else {
System.out.println("line count can not < 1 !");
}
}
}

step3:

public classChooseStragety {

　　privateStragety strategy;

　　public ChooseStragety(Stragety stragety)

{
　　　　this.strategy=stragety;
　　}

　　public void drawText()

{

stragety.drawText(String text, int lineWidth, int lineCount);

}

}