public void back() {
		
		if (this.curX - 1 >= 0) {
			this.lines[this.curY].deleteCharAt(this.curX - 1);
			this.curX--;
			for (int i = this.curY + 1; i < this.lines.length; ++i) {
				if (this.lines[i].length() > 0) {
					this.lines[this.curY].append(' ');
					this.lines[this.curY].append(this.lines[i]);
					this.lines[i].setLength(0);
				}
			}
			adjust(this.curY);
		} else if (this.curY > 0) {
			this.lines[this.curY - 1].deleteCharAt(this.lines[this.curY - 1].length() - 1);
			this.curY--;
			this.curX = this.lines[this.curY].length();
			for (int i = this.curY + 1; i < this.lines.length; ++i) {
				this.lines[this.curY].append(this.lines[i]);
				this.lines[i].setLength(0);
			}
			adjust(this.curY);
		}
	}