设计模式之装饰者模式-对装饰和内容一视同仁

最新推荐文章于 2025-04-24 10:42:11 发布

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本文介绍了一个使用Java实现的装饰者模式示例，通过定义一系列的装饰类来增强或修改现有功能，而无需改变其结构。具体展示了如何为字符串显示添加边框效果，包括侧边边框和全边框。

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十二、decorator装饰和内容一视同仁

public abstract class Display {
    public abstract int getColumns();
    public abstract int getRows();
    public abstract String getRowText(int row);
    public final void show(){
        for (int i = 0; i < getRows(); i++) {
            System.out.println(getRowText(i));
        }
    }
}

public class StringDisplay extends Display {
    private String string;

    public StringDisplay(String string) {
        this.string = string;
    }

    @Override
    public int getColumns() {
        return string.getBytes().length;
    }

    @Override
    public int getRows() {
        return 1;
    }

    @Override
    public String getRowText(int row) {
        if (row==0){
            return string;
        }else {
            return null;
        }
    }
}

public abstract class Border extends Display{
    protected Display display;

    public Border(Display display) {
        this.display = display;
    }
}

public class FullBorder extends Border {
    public FullBorder(Display display) {
        super(display);
    }
    public int getColumns(){
        return 1+display.getColumns()+1;
    }
    public int getRows(){
        return 1+1+display.getRows();
    }
    public String getRowText(int row){
        if (row==0){
            return "+"+makeLine('-',display.getColumns())+"+";
        }else if (row==display.getRows()+1){
            return "+"+makeLine('-',display.getColumns())+"+";
        }else {
            return "|"+display.getRowText(row-1)+"|";
        }
    }

    private String makeLine(char chars, int count) {
        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < count; i++) {
            buffer.append(chars);
        }
        return buffer.toString();
    }
}
public class SideBorder extends Border {
    private char borderChar;

    public SideBorder(Display display, char borderChar) {
        super(display);
        this.borderChar = borderChar;
    }
    public int getColumns(){
        return 1+display.getColumns()+1;
    }
    public int getRows(){
        return display.getRows();
    }
    public String getRowText(int row){
        return borderChar+display.getRowText(row)+borderChar;
    }
}

public class Test {
    public static void main(String[] args) {
        StringDisplay joanna = new StringDisplay("joanna");
        SideBorder sideBorder = new SideBorder(joanna, '@');
        FullBorder fullBorder = new FullBorder(joanna);
        joanna.show();
        sideBorder.show();
        fullBorder.show();
        Display composite=new SideBorder(new FullBorder(new SideBorder(new FullBorder(new StringDisplay("zhouzhou")),'$')),'#');
        composite.show();
    }
}